I'll try. It's obviously done on a computer. So the big thing here is software. There are many software programs available. The most popular is Photoshop, for non professionals getting Photoshop Elements 2 is the best bet. PaintShop Pro is another, as is Gimp, MS Picture-It.

The key to the software is the ability to layer. Basicly you want to beable to put one picture on top of another and have them look good. On top of layering...there is things like croping, color correction, advanced selection. The point is, when you find your program, then just google on how to use it.