After you get your mask, you leave the starting town and travel to Santa Luchita. Head up the long stairs. Run right a little, jump on the red wall with the wanted posters. and go up the ramps. You'll met a wrestler who tells you about his special move; "the toilet flush." Past him is a building labeled "combo chicken's Gym" with a flashing sign that says "New Combos." Enter it.
The combo chicken will tell you what buttons to press.