Go into your garage and locate your purple smart button which is normally located behind the back light cover. If you do not have a back light cover look for the antenna wire. Now that you have located the purple smart button its time to program your Liftmaster 377LM keypad.
Step 1:Push the purple smart button in and let off.
Step 2:Now open up the lid on the 377LM keypad and type in your 4 digit code then hit enter.
Your lights on your opener should have blinked on and off letting you know your keypad has been programmed.
Now it’s time to mount your keypad.
Step 1:Put the first screw in the center of your jamb how ever high you want to mount it.
Step 2:Put your 377LM keypad on that screw and pull it downward.
Step 3:Pop open the battery cover and you will see where the second screw goes. Make sure your 377LM keypad is straight then put the second screw in.