okay, first thing you have to have is your "layers" window showing. If it's not you can go to the window menu and show it. You have to be in RGB mode to use layers.
With the backgroun being the original skin, hit the "new layer" button at the bottom of the layers window. Use the lasso tool. You can still see the bottom layer but you're not working directly on it. You never want to work directly on the original layer, because you'll need it.
So, take the lasso tool so you have the right shape, then do what you want on the other layers. Create more as you need (I think you're limitd to 50 total). Example, use the lasso tool to get an outline of the wings, then use a paint bucket and fill in the wings on a different layer. Don't forget to name your layers so you can understand them.
From there it's basic photoshop skills. There are lots of webpages and books and the like that have general use tips.