Rag quilts are really easy. Even if you get the pieces a little too big or too small, you can still make it work. Check your measurements and cut the pieces down if needed. Otherwise, you can just fudge them together, since you'll be "ragging" the edges and it won't show.
I KNOW you can do this!!! Just read through ALL the directions first. Take your time!! You'll get it! You go girl!!!