When I used to be a religious atheist I used to look down on people who talked about faith in God. How can you have faith in something you can’t see? It seemed to me that having faith meant parking your brain at the door.
What is faith? In the ancient Greek language the word translated into the English word faith is also translated interchangeability as belief and trust. We believe and trust all sorts of things. When you are driving down the road you trust that that painted yellow line down the middle will prevent the person coming towards you won’t cross over it and run into you. We also have some faith in family and friends – trusting they will do what they say they will do. These faith experiences come from experience and knowing the person.
How can you have faith in God? The same way your faith grows in another person; you have to get to know God. How do you do that; how do you get to know an infinite and invisible being? The Bible claims that Jesus is the exact representation of God, Jesus is recorded saying that when we see him we are seeing God the Father, and the claim that Jesus is actually God is all over scripture. Try getting to know Jesus through the Gospels (Matthew, Mark, Luke and John); reading through the account of his life. Put yourself into the story, imagine yourself walking beside Jesus, listening to him and doing what he says to do. You will be surprised how your faith will grow.