You could always download gimp. It's free and is basically photoshop. Personally I like it better and it's easier to use and you can just download all the things you need :)

I don't think it's as good as downloaded photoshop, but I use pixlr.com/editor
Tips for use: ALWAYS save as a png, check out other brushes (there's splatters, cracks, etc), free transform and free distort are great
Have fun with it~