Also, you can get very practical with a tracker to learn composing on the fly. If you don't know how the program works, follow the tutorial. From there, you can just play with it and your music becomes better with every song. Don't look for the technical knowhow, look for what you love to hear and create that.
It works best if you just cut everything in sections. So don't try to create that entire song you hear in your head, but create a bass line, create a drum track, create a melody etc...
And once you have something in your song, just find sounds that fit with what you already have and enter notes in and experiment.
Eventually you can try to create an existing song from scratch to get better at converting an idea to a song.
