The sincerity of Alma’s conversion is manifest in his unremitting efforts to share that taste of heaven with others. Being cleansed from sin was instantaneous, but the actual process of living the gospel—of finishing the repentance process—required the rest of his life. Alma devoted the rest of his life to undoing the damage he had done, leading others back to Yahweh.
Alma shares this personal experience with Helaman for two reasons. The first would be to explain his life; but since Helaman was his son, he probably already knew these details. Second, the story itself is meant to be instructive—not in its spectacular details which we do not hope (or fear) to endure but as a model of how we must be reconciled to God. In our sinful state, we must follow Alma’s pattern, first recognizing and feeling true remorse. To effect a change in our natures, we must then call on Christ and accept his atoning sacrifice. The infusion of the Holy Ghost assures us that our sins are forgiven. The final step is to implement that experience in our lives to benefit not only ourselves but others.