That's the rescue operation going on. All because of what Christ has done. He makes it available to us through Jesus Christ. Our part is to accept this gift. God doesn't force it on people who don't want it.
Faith is, in simple terms, belief and trust.
We believe that we need to be rescued, and we believe that Jesus Christ does it for us. We trust our lives and our future to him. We accept the fact that we have sinned, that we have become enemies of God. We are incapable of changing our sinful hearts, but through faith in Christ, we are changed by God himself from enemies to friends, from aliens to family members. God saves us as a gift of mercy.