Cut the paper to a size that is larger than the headstone and tape it down tightly so that it doesn't move. Be sure to cover the whole stone so that you don't accidentally slip and mark the headstone with your wax or crayon. Start rubbing the outside edges which will make a frame and then work your way in. Do not rub too hard otherwise you will rip the paper and put the wax or crayon onto the headstone. If the result is not dark enough go over it again until it is dark to your liking.
Some people prefer dark rubbings and some prefer light rubbings.
It's just a matter of personal preference. When you are finished rubbing, carefully remove the paper and tape from the headstone being careful not to tear your rubbing. You are now finished. That's all there is to it.