You're going to need to cut off two strings from each color. Each string should be about 2 1/2 feet long, maybe a bit longer if you're making an anklet. I usually just eyeball it and it works fine...
... I suggest just cutting 2 yards of each string and folding it in half, and I'll show you why.
Your bracelet might not look like much at first, but pretty soon it'll start to take shape. Dont give up! When it's as long as you want it, tie it and cut off the excess string.
Hope this wasn't too confusing :) leave comments/questions/concerns!