How to program my garage remont from my hummer garage door is an overhead?

look in car manual under homelink, it should say to erase the factory test hold the desired button for 20 sec then program hummer remote by holding the remote and hummer remote until light stops blinking 5 to 10 sec next go to the learn button at the back of the motor in the garage then within 30 seconds u must hit the car button three times