It is “the knowledge of the truth...which leadeth them to faith on the Lord, and unto repentance, which faith and repentance bringeth a change of heart unto them.” (Helaman 15:7)
Repentance comes after an invitation from the word of God through his servants. A holy man named Alma explained that his being born again came as a result of being called to repentance by an angel:
For because of the word which he has imparted unto me [through an angel], behold, many have been born of God, and have tasted as I have tasted, and have seen eye to eye as I have seen; therefore they do know of these things of which I have spoken, as I do know; and the knowledge which I have is of God. (Alma 36:26)
Alma alluded to his extensive experiences preaching the gospel to others. All who believed and repented were born of God, as is always the case.
In another account, Alma describes the pattern, recounting how his father (also named Alma) came to repent and be born again:
7 Behold, [God] changed their hearts; yea, he awakened them out of a deep sleep, and they awoke unto God. Behold, they were in the midst of darkness; nevertheless, their souls were illuminated by the light of the everlasting word; yea, they were encircled about by the bands of death, and the chains of hell, and an everlasting destruction did await them.
11 Behold, I can tell you—did not my father Alma believe in the words which were delivered by the mouth of Abinadi? And was he not a holy prophet? Did he not speak the words of God, and my father Alma believe them?
12 And according to his faith there was a mighty change wrought in his heart. Behold I say unto you that this is all true.
13 And behold, he preached the word unto your fathers, and a mighty change was also wrought in their hearts, and they humbled themselves and put their trust in the true and living God. And behold, they were faithful until the end; therefore they were saved.
14 And now behold, I ask of you, my brethren of the church, have ye spiritually been born of God? Have ye received his image in your countenances? Have ye experienced this mighty change in your hearts? (Alma 5)
The process laid out by Alma was: 1) the word of God was preached by one of his servants, 2) Alma’s father believed what was said and faithfully repented of his sins, 3) he preached the word to others, who also repented. They all were born again.
We see this pattern repeated again and again. On another occasion, a servant of God named Ammon taught the gospel to a king named Lamoni who repented of his sins, then Lamoni taught the word of God to others who also repented, and all of them were born again:
31 And he, immediately, seeing the contention among his people, went forth and began to rebuke them, and to teach them the words which he had heard from the mouth of Ammon; and as many as heard his words believed, and were converted unto the Lord.
32 But there were many among them who would not hear his words; therefore they went their way.
33 And it came to pass that when Ammon arose he also administered unto them, and also did all the servants of Lamoni; and they did all declare unto the people the selfsame thing—that their hearts had been changed; that they had no more desire to do evil. (Alma 19)
When a person reconciles their thoughts, desires, and actions to all they understand about God, they are freed from the guilt of their past sins, through faith in the words of Jesus Christ, who promises forgiveness of sins to all who forsake their sins. As Alma described of his own repentance:
28 Nevertheless, after wading through much tribulation, repenting nigh unto death, the Lord in mercy hath seen fit to snatch me out of an everlasting burning, and I am born of God.
29 My soul hath been redeemed from the gall of bitterness and bonds of iniquity. I was in the darkest abyss; but now I behold the marvelous light of God. My soul was racked with eternal torment; but I am snatched, and my soul is pained no more. (Mosiah 27)
All who reconcile their lives to God’s will, as far as they understand it, are forgiven of their sins and will be born again. They learn of God’s will through another who knows him more than they do.