Upload & Sell: On
I'm at work now so I can't use PS to illustrate my reply, but I may not need to. Let's start with the basics:
How familiar are you with the use of layer masks? If the answer is, "not very," then googling "photoshop layer masks" will turn up a boatload of how-to tutorials such as this one
If you already understand the concept, we can move forward. Let me know when you're ready for the next step.