This is from my 02 manual:
STANDARD PROCEDURE - SETTING
TRANSMITTER CODES
(1) Turn off the engine.
(2) Erase the factory test codes by pressing buttons
1 and 3. Release the buttons when the two
green lights begin to flash (about 20 seconds).
(3) Choose one of the three buttons to train. Place
the hand-held transmitter within one inch of the universal
transmitter and push the buttons on both
transmitters. The green dot below the house symbol
will begin to flash slowly.
(4) When the red light on the universal transmitter
begins to flash rapidly (this may take as long as
60 seconds), release both buttons. Your universal
transmitter is now “trained”. To train the other buttons,
repeat Step 3 and Step 4. Be sure to keep your
hand-held transmitter in case you need to retrain the
universal transmitter.