I believe you push on the brake pedal with the truck running and trailer hooked up. Move the lever all the way over. Turn the knob until it says 6 or 7 (can't remember). Then, on a flat area like an empty parking lot, get up to 20-25 mph and stop. If it locks up, turn the number down. I usually push the button to be set on 2, 3 if I'm in the mountains. I like to feel the trailer brakes just a little before the truck brakes. Try Tekonsha's web site if you misplaced the directions, they may have them online.