The word "believe" in the Bible means more than simply agreeing in our minds that something might be true. It means "trust"—that we believe so strongly in God that we are willing to commit our lives to Him and live the way we know He wants us to live.
Suppose you were walking along a path and you came to a bridge which crossed a deep canyon. You might look at it and believe that it would hold you, and you might even see other people walking across it so you know it would hold your weight. But so far, your "belief" in the bridge is only in your head. When do you really believe the bridge will hold you? You only really believe it when you are willing to commit your life to it and actually walk across it.
It is the same way with Christ. Yes, we can believe that God exists, but God wants us to come to know Him personally. And He has bridged the gap between us by sending His Son to remove the barrier of sin and become that "bridge." To believe in Christ is to commit our lives by faith to Christ—to trust Him personally as our Lord and Savior. Our prayer is that you will come to truly believe in Christ.