How to Use the Photoshop Clone Stamp Tool
From Eric Miller, former About.com Guide
The Photoshop clone stamp tool allows you to copy one area of an image and copy it onto another area. In order to practice this, open a photo in Photoshop. To do this, go to file>open, browse to the photo on your computer, select the filename, and click open. Any photo will do for practice, but if you have one that needs some retouching use that one.