easiest way is just play with Photoshop...
it is extremely robust.. so it will take time..
no one can teach you ..
you can watch all the videos you want.. you'll never learn unless you just play with it.. you'll start to discover things.. just like anything.. you have to want to learn
F.Y.I
i have a few unused serials for Photoshop CS5 that will work with the Trial versions posted on Adobe.com