I would suggest getting the Scott Kelby book for your version. He has produced books on every version on Photoshop for quite a few years and if you follow along with his book, you will learn a lot.
Also agree with MF above, that youtube has some great tutorials, but you need to know what to search for to begin with, as it is better to search for 'photoshop levels tutorial", or "photoshop unsharp mask tutorial" than just photoshop tutorials.
You can also ask here on AP. We have some tutorials in our
Tutorials forum already, and members are often willing to help out with instruction and advice if you ask.