Once you find the button on your opener you can use it to program new devices. If you get a new remote or install a wireless keypad you will need to program the two together.
Your opener should have a LED indicator light to communicate to you while you are programming the new devices. When you clear the memory on the opener, the LED will light up and stay that way for 30 seconds. Once it goes off, you know the unit is cleared out. Then you will need to push the learn button again to program it to the new devices.