At the very basics, the making of a Christian is a simple process. Someone tells them about Jesus, they put their faith in Him, and they go about the rest of their life. But there is much more to the story than that.
Before the foundations of the world, God had already planned out the salvation of every person who would ever believe in Him. He had already set forth a plan to reconcile mankind to Himself, and that was through the life, death, and resurrectino of His Son, Jesus Christ.