Acts 2 describes who is should be baptized. This is referred to as believer's baptism.

Those who have placed their trust in Jesus Christ alone for the forgiveness of their sins are candidates for baptism; those who accept His message. (Acts 2:41)

Baptism shows a beautiful picture of the death, burial, and resurrection of Jesus.

The purpose is to symbolically profess new life through salvation in Jesus Christ.

"What shall we say, then? Shall we go on sinning so that grace may increase? By no means! We died to sin; how can we live in it any longer? Or don't you know that all of us who were baptized into Christ Jesus were baptized into his death? We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life." Romans 6:1-4

The Greek word "baptize" means to immerse under water. It is Biblical to immerse; there are other Greek words for pour and sprinkle, but they are never used in the New Testament for baptism.