The Catechism in Questions & Answers

649. What must a person do in order to have his sins forgiven?

In order to obtain forgiveness for one’s sins, the following are required:

the person must believe in Jesus Christ as his Redeemer (cf. John 8: 24).
in addition, one must believe that the forgiveness of sins is proclaimed by the Apostles.
it is also necessary to acknowledge that one has sinned, thereby incurring guilt, and that one is thus in need of grace.
the person must have the desire in his heart to be reconciled with God. n the sinner must regret his sins and acknowledge this before God in the Lord’s Prayer: “And forgive us our debts...”
one must make the earnest resolution to overcome one’s weaknesses and mistakes.
the sinner must have the desire to be reconciled with those who have wronged him and thereby incurred guilt with him.

“Therefore I said to you that you will die in your sins; for if you do not believe that I am He, you will die in your sins.”
John 8: 24