In Acts 2, Peter the apostle gave a sermon to the people who had witnessed and assented to the crucifixion of Jesus. After being convinced that they had not only murdered an innocent man but that this man was the Son of God, they asked in verse 37, "Brethren, what shall we do?'
Peter replied in verse 38, "Repent and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit."
In verse 41, "So then, those who had received his word were baptized; and that day there were added about three thousand souls."
Baptism is the act by which a person is united with Jesus into His death. It is a burial with Christ. "Therefore we have been buried with Him through baptism into death, so that as Christ was raised from the dead through the glory of the Father, so we too might walk in newness of life." Romans 6:4
Examples can be found in the book of Acts of people becoming Christians. There is the Ethiopian eunuch in 8:27-39, a woman named Lydia in 16:13-15 and a jailer in 16:23-34.
Faith demonstrated by a simple act of obedience is the entryway into Christ.
"For all of you who were baptized into Christ have clothed yourselves with Christ." Galatians 3:27