It's as Easy as "A-B-C"
Admit you have sinned. The Bible teaches that all of us have sinned and fallen short of what God intended for us. "For all have sinned, and come short of the glory of God."(Romans 3:23) You need to admit that you have sinned and that Christ is the only One Who can remove all of your sins from you. Because of sin we cannot have fellowship with God. "But your iniquities have separated between you and your God, and your sins have hid His face from you, that He will not hear." (Isaiah 59:2).
Believe that Christ died and rose again to pay the penalty for your sin. "For He hath made Him to be sin for us, Who knew no sin; that we might be made the righteousness of God in Him." (II Corinthians 5:21). Believe that Jesus wants to give you eternal life as a free gift. "For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord." (Romans 6:23). You must believe that He Alone can get you to heaven, not any of the good things you have done.
Call on Christ in simple faith and ask Jesus to save you. "For whosoever shall call upon the name of the Lord shall be saved." (Romans 10:13).
Pray something like this: LORD, I ADMIT I HAVE SINNED, I BELIEVE CHRIST DIED FOR ME, PLEASE SAVE ME IN JESUS NAME. AMEN.