A hint, the clamps on the sides are too tight. The grain should not be pulled out of place. The clamps simply holds the side so the side can't swing as you quilt near the side. It is not to hold your backing tight. The clamps only clamp on to the backing which is larger than the top. But for practice, not problem.
Have fun quilting. Pretty soon the whole set up will become faster and easier. It takes a little to get that muscle memory thing going so don't be hard on yourself the first time you quilt. You will get better and better and better with every quilt you make.