"Therefore, I would that ye should know, that after the Lord had shown so many marvelous things unto my father, Lehi, yea, concerning the destruction of Jerusalem, behold he went forth among the people, and began to prophesy and to declare unto them concerning the things which he had both seen and heard."
The Lord in His mercy showed the things that would happen to Jerusalem according to His words. the Lord warned Jerusalem before they were destroyed and because of sin they did not heed the word of God and Jerusalem was destroyed.
After Lehi had learned all of this he went to the people and as had the prophets before him preached to them the word of the Lord about the destruction of Jerusalem. He spoke of all the things he had learned, trying to convince them of their evil and carnal ways. Being a missionary is not easy under any circumstances, especially if you have to tell people that they are doing evil things. I am impressed with Lehi and his desire to help people come to the truth and find the way to right.