It’s very simple. Once you have heard the gospel message and believe it is true, you simply say, I believe this is true and I want to give my life to Jesus Christ for my personal salvation and to serve him the rest of my life*.
You can pray a simple prayer confessing that you are a sinner, that you are turning away from all your sin and committing your life to follow Jesus, and then ask God to forgive you and make you His child.
There is no magic in the words of the prayer. You can use whatever words you want. What matters is the act of your will-your sincere intent of giving yourself up to God and accepting Jesus’ sacrifice for your sins, asking forgiveness and deliberately intending to live for Jesus for the rest of your life. That is your step of faith.
How important is faith to being a follower of Jesus? It’s essential. One passage in the New Testament says: And it is impossible to please God without faith. Anyone who wants to come to him must believe that God exists and that he rewards those who sincerely seek him (Hebrews 11:6).
And back in the very first book of the Bible-Genesis-we read, And Abraham believed the LORD, and the LORD counted him as righteous because of his faith (Genesis 15:6).
So to become a follower of Jesus you need to have faith, and as a Christian you continue to live in that faith.