Christianity has premises:
1.  There is a God who wants to be our Father.
2.  He communicates with us in prophecy, and in His Word.
3.  There are two forces in the human world:  Good and Evil.  And we know the difference.
4.  We choose evil, and there is no way for us to undo that--no matter how much good we do.
5.  We are doomed.  God, who is righteous, placed a penalty on sin:  Death. 
6.  If we are ever to be pure, we have to totally eliminate all the bad we have done.
7.  We are incapable of doing that on our own.
8.  God devised a plan to do that.  A sacrifice for sin.
9.  He became a man and died in our place.  Jesus was that man--God incarnate.
10. He did that because for some reason, he loves us.

I will never understand why he loves us.  We are unlovely.  He loved us first--in all our wretched condition.  He took pity on us and extended mercy.  Why?  Why would He do that?

God has conditions for the forgiveness of sin.
1.  You must recognize your condition and repent from your sins.
2.  You must give him control of your life.

Romans 10:9 "That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved."  Believing that Christ is raised from the dead is part of it.  He is alive.

1 John 1:9 "If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness."

He then forgives us. And gives us:  1. His Spirit, 2. Eternal Life. 3. A clean heart.  Amazing Grace!