Take a towel and run it through the washing machine.
Place the wet towel in the dryer just long enough for the towel to get warm, but not dry.
Place a dry towel over the wrinkled area on the rug.
Place the warm towel on top of the dry towel.
Place a heavy object on top of the towels to apply pressure, such as a small piece of furniture, phone book or even a few more area rugs.
Let the heat remove the crease. Repeat this process if necessary.