When you pull the tab, the pages flip up and under each other. This is a great time to use a Scor-it Board or other scoring tool. It keeps things very precise and neat. If you don't have one, don't worry. You can just use a ruler and a bone folder or dry-embossing stylus. First, cut out 5 squares that are 2.5 inches x 2.5 inches. These are the "pages" of your waterfall fold. You'll also need a 10"x2.5" strip of cardstock. This is what your "pages will be adhered to. Lastly, you'll need a base for your waterfall fold to adhere to. I used a strip that's 1.5"x6 inches (it's the one with the chipboard circles on it).
Tomorrow, I'll post some specific, step-by-step instruction for the waterfall fold. Start with this for now.