Putting your faith in Jesus Christ is more than just believing that God exists (
James 2:19). Having faith or becoming a Christian means that you have put your full trust in Jesus as your Savior—you believe Jesus is God’s Son, that he died for you on the cross to pay the penalty for your sin (bad/wrong things we do that are against God's nature), and was raised to life again. By believing and trusting in these truths outlined in the Bible, walking away from your sin, and receiving God’s free gift of grace and forgiveness, you are saved (
John 3:16 and
Romans 10:9). Most often a person will pray (talk to God) to express that they believe all of this. If you’ve done this—way to go!
Now, once you have been saved, God starts to transform your old life into a new life in Christ (
2 Corinthians 5:17), which means we become more and more like Jesus. Signs of this change start on the inside and eventually lead to outward actions. Inwardly, you should see what we call the "fruit of the Spirit" developing in your life: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control (
Galatians 5:22-23). Outwardly, you will start to live out your faith by doing good things, like showing love to others, serving, and living generously. Again, doing good things is not what saves you, it's simply a sign that you are living in your new life in Christ by doing and caring about the things Jesus did and cared about.