1. Turn the first knob to select credit card or cash 2. The second knob is funny, it serves no real purpose - turn as you may, the size of the schlong that's about to puncture your pooper remains at 12" 3. Sit back and enjoy the feeling. A little soreness is to be expected at first, but within a week you'll be as adept at this as a porn star - you may even take the next step and buy an ipod.how do they work?!?!?!