It may be helpful to see what your frame is like.
Mine, I have muslin nailed on the two sides that roll. I have the center point of each rail marked with permanent marker so I can center my quilt into the frame. When I use the frame, I add approximately a yard to the backing, so I have enough. Then, I roll the whole thing on one side, and roll it to the other side as I advance. I don't think it's a good idea to use staples or nails on your backing fabric. Better on fabric that will stay on your frame.