So there’s a process here. First he says to “repent.” Repenting is just a theological term for changing your mind and heart to turn towards God. It means realizing that you have sin in your life, that you regret those sins, and then resolving to follow God. But it’s not a one-time event; it’s a way of life. Being baptized means you are inviting God to live in you so He can help you make this life-long change.
After you take that first step of repentance, then comes baptism. Being fully submersed in water makes for a powerful metaphor: You’re burying the old you in a watery grave; the new you who comes up out of the water is a new creation (2 Corinthians 5:17 2 Corinthians 5:17Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
American King James Version×). After you come up out of the water, a minister of Jesus Christ lays hands on you and prays for God to give His Holy Spirit (Acts 8:14-17 Acts 8:14-17  Now when the apostles which were at Jerusalem heard that Samaria had received the word of God, they sent to them Peter and John:  Who, when they were come down, prayed for them, that they might receive the Holy Ghost:  (For as yet he was fallen on none of them: only they were baptized in the name of the Lord Jesus.)  Then laid they their hands on them, and they received the Holy Ghost.
American King James Version×). God gives it to you then—and no, it doesn’t come down like a dove or with tongues of fire. You probably won’t feel dramatically different after you come out of the water. You know you have received it because God promises to give it to you when you repent in faith and follow the steps outlined.
Once you have the Holy Spirit, you have access to something incredible: the very power and essence of God. It is a spirit of “power, of love, and of a sound mind” (2 Timothy 1:7 2 Timothy 1:7For God has not given us the spirit of fear; but of power, and of love, and of a sound mind.
American King James Version×). The power of God is what you can draw on to make bold and dramatic decisions in your life. The love of God is what you can draw on to let go of the hurts caused you by others, and to love them back. And the sound mind of God is what you can draw on to be calm, disciplined and unafraid in the face of the greatest, most challenging trials of life. With God’s Spirit, you can lean on God to help you beat back the negativity of the world, to shoulder the worst disappointments, to continue on in the face of withering sorrow, and to destroy the hatred of Satan.
Notice that I said that with God’s Spirit, you can do all those things. Receiving it does not make you perfect. It does not pave the road of life with gold. If you think about all the people you know who have been baptized, there are no doubt people who come to mind who have done things wrong; or who have hurt you; or who are mean. Everybody is fighting a hard battle. Nobody is perfect. We all make mistakes. But leading a life of repentance means we can and should depend on the power of the transformational Spirit of God every single day to acknowledge those mistakes and then fix them.
If you are thinking about baptism, United Church of God has ministers around the world who can answer your questions. Find a congregation near you and visit, or call the pastor there. He can give you good counsel on it and guide you through the process of deciding when the time is right for you to accept God’s gift of salvation by becoming baptized. United also has a helpful booklet on the subject called Transforming Your Life: The Process of Conversion.