Alma Ch45

Helman was the oldest son of Alma the Younger and takes over writing records, and most of the rest of book of Alma is Helman's records, at least until ch62. This is the chapter that describes how Alma passes the plates along, the 'death' of Alma, and how the church is doing.
After the Nephite victory, Alma approaches Helman to find out if he is ready to take upon the responsibility of the sacred records by asking if he believes in them and Jesus Christ and is willing to keep the commandments (v1-8). Helman says yes to all his father is asking and is given the plates to write his fathers prophecies and eventually the things the Lord wants him to write (v9). The prophecy that Alma tells Helman to record is about the dwindling in unbelief of the Nephites after Jesus Christ comes because of their works of darkness, lasciviousness, and many sins against the great light and knowledge (v10-12). There will be a time when their will no longer be anyone known as Nephites, but only Lamanites who hunt down the disciples of the Lord until they are extinct (v13-14).
>>side bar>> if you've ever read the story of the Book of Mormon, this prophecy totally happens in 4th Nephi, and we will get there, I promise.
Alma then uses his last days on earth to bless his sons, the earth, and the church for righteous' sake that there might not be any allowance for sin and that all may stand fast in the faith (v15-17). The story of his 'death' is suspicious because he left Zarahemla heading toward Melek and was never heard of again, but everyone speculates and things he was translated because he was so righteous, and I'm sure the Lord took care of him (v18-19).
So, Helman becomes the leader of the church and goes to preach to the people because they've been through a lot will all the wars and contentions with the Lamanites (v20). He went with the purpose of regulating church doctrine and correcting any dissension by appointing proper teachers and priests to teach the people in every city (v21-22). Unfortunately, the people had a hard time accepting the new leadership and became prideful and greedy instead of continuing to thank the Lord for their blessings (v23-24).