Layers can be confusing when you start out, but with a little bit of experimenting they do become straight forward – honestly! There's an excellent introduction to them in the video tutorials here:
If I were you I'd do what I did which is to work your way through all the video tutorials and try each technique with one of your own pictures as you watch. It's a real eye-opener as to just how powerful and easy to learn the programme is, and it's great fun as each tutorial will make you a) more skilled and B) really excited about working on your pictures.