This should be in the owners manual, but here goes. To start, press the two outside homelink buttons down and hold them till the red light blinks rapidly. This clears out any codes stored in the system. Then press, at the same time, your remote garage door opener and the button you want to program. Hold the buttons down till the light blinks rapidly again. If the homelink button works by itself, you are done. If not, go up a ladder and look at the garage door motor unit. There should be a "learn" button (red). Press this and a small light in the motor unit will light or blink. You have about 30 seconds to press your homelink unit in the car again (hold it down for about 20 seconds). The next time you press the homelink unit, it should be working correctly. If not, do it all over again (sometimes it takes a second try). Easier to do with two people.