HERE with And now I speak unto you, Joseph. (v.1)
Chapter 3 is all about Joseph. Joseph Smith, Jr., that is, along with three other Josephs and lots of loin fruit. (See the LDS Seminary Manual's section on 2 Nephi 3 to see that I'm not making this up.)
Since it's easy to get them confused, here's a list of the four Joseph's in this chapter.
1. Jacob's son, Joseph, in the book of Genesis
2. Lehi's son, Joseph
3. Joseph Smith, Sr.
4. Joseph Smith, Jr.
The Joseph Lehi is speaking to in this chapter is is Lehi's youngest son (#2), who was born in the wilderness and got hungry on the voyage to America.
-I am a descendant of Joseph who was carried captive into Egypt. (v.4)
Next we meet Joseph #1, the one from the Genesis in the Bible. Lehi discovered that he was a descendant of this Joseph by reading from the plates of Lehi (that Nephi stole from Laban after murdering him). So Lehi was a fruit from Joseph #1's loins.
-Joseph truly testified, saying: A seer shall the Lord my God raise up, who shall be a choice seer unto the fruit of my loins. (v.6)
Joseph #1 (who was supposed to have lived ~1500 BCE) prophesied about another Joseph (#4), a descendant of his, who would live 3300 years later in New York State (Joseph Smith, Jr.).
He will be a choice seer, esteemed highly, and shall do "a work of great worth." He will be great in God's eyes, like Moses, and will do God's work. He will bring forth God's word, confound false doctrines, establish peace, and bring knowledge in the latter days. All those who seek to destroy him will be confounded. He will be like God and will bring God's people to salvation. He will have exceeding faith, work mighty wonders, and do what is great in the sight of God.
Don't look for these prophecies in Genesis, though, or anywhere else in the Bible. They used to be there, but they were removed by the Catholics. But, lucky for us, they were restored by Joseph Smith, Jr. in the Joseph Smith Translation of the Bible (Genesis 50:24-38).
-The fruit of thy loins shall write; and the fruit of the loins of Judah shall write; and that which shall be written by the fruit of thy loins, and also that which shall be written by the fruit of the loins of Judah, shall grow together, unto the confounding of false doctrines and laying down of contentions, and establishing peace among the fruit of thy loins. (v.12)
The fruit of Joseph's loins shall write (translate?) the Book of Mormon and the fruit of the loins of Judah shall write the Bible. The Book of Mormon and the Bible will grow together confounding the false doctrines of the Catholics and other members of Satan's church.
-His name shall be called after me; and it shall be after the name of his father. (v.15)
And finally, Joseph #4 arrives! Joseph Smith, Jr. was named after his father, Joseph Smith, Sr. (Joseph #3), who was named after the Joseph of Genesis (Joseph #1).
-There shall rise up one mighty among them, who shall do much good, both in word and in deed, being an instrument in the hands of God, with exceeding faith, to work mighty wonders, and do that thing which is great in the sight of God (v.24)
Just in case it isn't completely obvious by now, Joseph Smith Lehi is praising Joseph Smith here.
Four Josephs and the fruit of many loins

3:1-25
1 And now I speak unto you, Joseph, my last-born. Thou wast born in the wilderness of mine afflictions; yea, in the days of my greatest sorrow did thy mother bear thee.
2 And may the Lord consecrate also unto thee this land, which is a most precious land, for thine inheritance and the inheritance of thy seed with thy brethren, for thy security forever, if it so be that ye shall keep the commandments of the Holy One of Israel.
3 And now, Joseph, my last-born, whom I have brought out of the wilderness of mine afflictions, may the Lord bless thee forever, for thy seed shall not utterly be destroyed.
And now I'm talking to you, Joseph, my last-born son. [1]
4 For behold, thou art the fruit of my loins; and I am a descendant of Joseph who was carried captive into Egypt. And great were the covenants of the Lord which he made unto Joseph.
You're the fruit of my loins.
I'm a descendant of Joseph who was carried captive into Egypt. [2]
5 Wherefore, Joseph truly saw our day. And he obtained a promise of the Lord, that out of the fruit of his loins the Lord God would raise up a righteous branch unto the house of Israel; not the Messiah, but a branch which was to be broken off, nevertheless, to be remembered in the covenants of the Lord that the Messiah should be made manifest unto them in the latter days, in the spirit of power, unto the bringing of them out of darkness unto light -- yea, out of hidden darkness and out of captivity unto freedom.
He foresaw our day, and God promised to raise up, in the latter days, a righteous people from his loins.
6 For Joseph truly testified, saying: A seer shall the Lord my God raise up, who shall be a choice seer unto the fruit of my loins.
Joseph said,
God will raise up a choice seer from the fruit of my loins. [3]
7 Yea, Joseph truly said: Thus saith the Lord unto me: A choice seer will I raise up out of the fruit of thy loins; and he shall be esteemed highly among the fruit of thy loins. And unto him will I give commandment that he shall do a work for the fruit of thy loins his brethren, which shall be of great worth unto them, even to the bringing of them to the knowledge of the covenants which I have made with thy fathers.
God said to me:
I'll raise up a choice seer from the fruit of your loins.
He'll be esteemed highly by the fruit of your loins.
I'll tell him to do a work for the fruit of your loins.
8 And I will give unto him a commandment that he shall do none other work, save the work which I shall command him. And I will make him great in mine eyes; for he shall do my work.
I'll tell him to only do what I tell him to do.
He'll be great in my eyes.
9 And he shall be great like unto Moses, whom I have said I would raise up unto you, to deliver my people, O house of Israel.
10 And Moses will I raise up, to deliver thy people out of the land of Egypt.
He'll be great like Moses.
11 But a seer will I raise up out of the fruit of thy loins; and unto him will I give power to bring forth my word unto the seed of thy loins -- and not to the bringing forth my word only, saith the Lord, but to the convincing them of my word, which shall have already gone forth among them.
I'll raise up a great seer from the fruit of your loins.
He'll deliver my word to the seed of your loins.
12 Wherefore, the fruit of thy loins shall write; and the fruit of the loins of Judah shall write; and that which shall be written by the fruit of thy loins, and also that which shall be written by the fruit of the loins of Judah, shall grow together, unto the confounding of false doctrines and laying down of contentions, and establishing peace among the fruit of thy loins, and bringing them to the knowledge of their fathers in the latter days, and also to the knowledge of my covenants, saith the Lord.
13 And out of weakness he shall be made strong, in that day when my work shall commence among all my people, unto the restoring thee, O house of Israel, saith the Lord.
So the fruit of your loins will write and the fruit of the loins of Judah will write. [4]
And what is written by the fruit of your loins will grow together with what is written by the fruit of Judah's loins to confound false doctrines and bring peace to the fruit of your loins.
14 And thus prophesied Joseph, saying: Behold, that seer will the Lord bless; and they that seek to destroy him shall be confounded; for this promise, which I have obtained of the Lord, of the fruit of my loins, shall be fulfilled. Behold, I am sure of the fulfilling of this promise;
So Joseph prophesied saying,
God will bless that seer and whoever tries to destroy him will be confounded.
God promised my that the fruit of my loins would be fulfilled.
15 And his name shall be called after me; and it shall be after the name of his father. And he shall be like unto me; for the thing, which the Lord shall bring forth by his hand, by the power of the Lord shall bring my people unto salvation.
He'll be named after me, and his father will also have my name. [5]
16 Yea, thus prophesied Joseph: I am sure of this thing, even as I am sure of the promise of Moses; for the Lord hath said unto me, I will preserve thy seed forever.
17 And the Lord hath said: I will raise up a Moses; and I will give power unto him in a rod; and I will give judgment unto him in writing. Yet I will not loose his tongue, that he shall speak much, for I will not make him mighty in speaking. But I will write unto him my law, by the finger of mine own hand; and I will make a spokesman for him.
God said to me, "I'll preserve your seed forever."
18 And the Lord said unto me also: I will raise up unto the fruit of thy loins; and I will make for him a spokesman. And I, behold, I will give unto him that he shall write the writing of the fruit of thy loins, unto the fruit of thy loins; and the spokesman of thy loins shall declare it.
God also said to me,
I'll raise up a spokesman from the fruit of your loins.
He'll write the writings of the fruit of your loins to the fruit of your loins, and the spokesman of your loins will declare it.
19 And the words which he shall write shall be the words which are expedient in my wisdom should go forth unto the fruit of thy loins. And it shall be as if the fruit of thy loins had cried unto them from the dust; for I know their faith.
He'll write what I want him to write.
It'll be read by the fruit of your loins.
It'll be like he had cried to the fruit of your loins from the dust.
20 And they shall cry from the dust; yea, even repentance unto their brethren, even after many generations have gone by them. And it shall come to pass that their cry shall go, even according to the simpleness of their words.
And they'll cry from the dust, according to the simpleness of their words.
21 Because of their faith their words shall proceed forth out of my mouth unto their brethren who are the fruit of thy loins; and the weakness of their words will I make strong in their faith, unto the remembering of my covenant which I made unto thy fathers.
22 And now, behold, my son Joseph, after this manner did my father of old prophesy.
23 Wherefore, because of this covenant thou art blessed; for thy seed shall not be destroyed, for they shall hearken unto the words of the book.
It'll proceed out of my mouth into the fruit of your loins.
24 And there shall rise up one mighty among them, who shall do much good, both in word and in deed, being an instrument in the hands of God, with exceeding faith, to work mighty wonders, and do that thing which is great in the sight of God, unto the bringing to pass much restoration unto the house of Israel, and unto the seed of thy brethren.
25 And now, blessed art thou, Joseph. Behold, thou art little; wherefore hearken unto the words of thy brother, Nephi, and it shall be done unto thee even according to the words which I have spoken. Remember the words of thy dying father. Amen.
There will be a might man among them who will do good in word and deed. [6]
He'll have exceeding faith, be an instrument of God, work mighty wonders, and do what is great in God's sight.