There are hundreds (thousands?) of Photoshop books, ranging from almost insultingly simple to highly advanced. I would suggest getting one and using it to familiarize yourself with the myriad of controls in PS.
The Photoshop learning curve is fairly steep (Iknow, I'm still climbing) but just get familiar with the tools, and walk through some of the online tutorials, and pretty soon you start figuring things our for yourself.
There are some pretty good PS tutorials at Zymic.com