Churches are form of organization. They exist for a government of spiritual matters. Being that God is a God of order, it naturally follows that as man draws nearer to God that there would be a tendency to organize oneself into a church or an organized body of the followers of Christ.
This selection details how it was that Alma organized a church (or seven churches) in the land of Zarahemla after their return. As a part of this organization, the people of Limhi, who had also returned to Zarahemla, are instructed and received into the kingdom of God by baptism. As Alma is instructing the people of Limhi, the scriptures here point out that Alma did teach them that "they should remember that it was the Lord that did deliver them." (vs. 16) Upon being taught, Limhi and his people are desirous to be baptized.
Baptism was both a matter of organizational procedure as a gateway into the kingdom of God, but also a matter of personal covenant and a witness of the individual's commitment to follow God. In this way, the church of God was organized and established in the hearts of the people.