You respond with belief in Christ.
If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For it is by believing in your heart that you are made right with God, and it is by confessing with your mouth that you are saved.
You simply need to believe. That doesn't mean that you don't have any questions or that you understand everything. It simply means recognizing that you are indeed a sinner in need of a Savior. You recognize that you cannot be good enough for a perfect God on your own. And you understand that God loved you so much that he sent Jesus to save you. If you believe that, say so.
You respond by receiving Christ.
But to all who believed him and accepted him, he gave the right to become children of God.
Receiving Christ means acknowledging your belief in Christ, inviting him to come into your life, turning to God from your present way of living (repentance), and then beginning the adventure of letting God direct your life! And the moment you ask, it's done. Jesus has come in!