I'm starting here with a sheet of music, as the value of doing a skin is very apparent when it's important that script, faces etc. are right side up. If you're uncaring about that, or you want the image reversed, you can use a direct transfer instead.
Place the image you wish to turn into a 'skin' on a piece of palette paper,
Carefully peel the paper up from the palette support, and turn it over. Spritz it liberally with water, and