How do you know radio waves exist? You can't see them or feel them. You can't show me a photograph of them. Yet we know they exist because we can place a radio on a table, turn it on, and listen to the results of the waves hitting the radio.
How do I know Jesus exists? I can't see Him. I can't show you a photograph. Yet I know the effect He has had on my life. He is as real to me as radio waves are to you.
Because you don't believe something does not make it untrue.