This instruction is for 1996 Town Car, but I'm sure their similliar. I don't recall the manufacturer, but if you can remembwer, or maybe it's kinda embossed on the facia plate, they have a website that gives details of every different year, and car. It's Home(something) ?
Ok I remember'd it. Homelink
However, they took down their programming pages. They do have basic instructions posted there, and some support options as well.
from the 1996 book:
Universal Transmitter
The universal transmitter provides a convenient way to consolidate the functions of up to three individual hand-held transmitters into one universal transmitter.
The universal transmitter:
l will operate garage doors, gates, home/office lighting systems or even security systems and nearly any device that is controlled by radio frequency.
l will actually learn and transmit the radio frequency of up to three hand-held transmitters from any of the systems mentioned above.
l is an integral part of the LH inside visor and powered by vehicle's battery and charging system. No batteries are needed.
Programming
Before Programming
l Make sure batteries in the hand-held transmitter are not dead.
l Hold hand-held transmitter in the exact position described against the universal transmitter.
l Hold buttons for duration of the programming without interruption.
l For best results, place the hand-held transmitter end opposite the battery compartment against the universal transmitter when programming.
1. CAUTION: During this procedure the system being programmed will be made to operate. Make sure that people or objects are clear of the garage door or gate being programmed.
Decide which one of the three universal transmitter channels to be programmed (Button 1, 2, or 3).
2. Hold the end of hand-held transmitter button against the bottom surface of the universal transmitter so that the red light can be seen.
3. Using both hands, push both the hand-held transmitter button and the desired universal transmitter button. Do not release either button. Continue to hold both buttons through step 4.
4. Hold down both buttons until red light on the universal transmitter flashes, first slowly and then rapidly. This could take up to a minute or more. Release both buttons after light flashes rapidly.
The rapid flash means that the universal transmitter has been successfully programmed to match hand-held transmitter. The universal transmitter can now be used instead of hand-held transmitter.
Operation
To operate, simply press the appropriate button on the universal transmitter. The red light illuminates while the signal is being transmitted.
Clearing Program
To clear the universal transmitter of all previously programmed frequencies, simultaneously hold down buttons 1 and 3 until the red light begins to flash and then goes out. This will clear all three channels.
Individual channels cannot be cleared but can be reprogrammed at any time by implementing the programming procedures as outlined.