Learn to hear a sound and pick it on your instrument. Then, learn to hear and play a few sounds. Sing them before you play them to learn quicker and improve your pitch. Start down this road and eventually you’ll be playing the songs you love without searching for sheet music first.
NoSheet is a simple ear trainer. It focuses on strengthening the connection between a sound and the movement needed to make the sound. That’s it. But, in the meantime, you might as well learn some music theory. See for yourself how small the difference between the scales you’ve heard all your life and the scales you’ve never heard really is.