Once a priest of the wicked king Noah, he was converted by Abinadi and ever after taught the gospel with great power.   He taught the people secretly at the Waters of Mormon and eventually fled with his people into the wilderness. They buildt a city (Helam) but eventually were discovered and put into bondage by the Lamanites under the rule of Amulon. The Lord helped Alma and his people escape to Zarahemla where king Mosiah son of Benjamin gives him authority over the church.  

He is the father of Alma the younger.

Mosiah 17 - 29