Try to get the kind of wax that comes in flake or pellet form. It will melt a lot quicker. If your wax comes in blocks, cut it into smaller pieces so that it melts quicker. You will need to add wax to your candle. Many people find that candles made from pure crayon do not burn well. The wax will "shrink" when you melt it, so you will need the extra wax.

Summary:
Measure out enough wax to fill your candle holder, plus some extra and set it aside.