Problem with photoshop?

One of the best ways to do this is to use a layer mask. Just select the layer you want to edit, then go to the bottom of the layers palette and there's a on "Add Layer Mask". Click that then make sure you click on the layer mask you just added to that layer. Then select your brush tool with the color black and start painting over what you don't want. The good thing with this is if you go over something you didn't want to take out just select the white and and go back over it and it will come back. It works better than the eraser cause with the eraser you might take out something you wanted to keep.It's pretty easy once you get used to it. And if you want tutorials go to Good-Tutorials.com, there's about 1435 tutorial for photoshop on there.