It's a dealer installed option. I have it and they used to have the instructions on the audiovox website, but I couldn't find the link.
Luckily I printed it out.
1.Enter the vehicle & turn ignition to "on"
2.Flip the valet switch (red button) on-off-on-off-on then off
3.The led will flash once and the alarm will chirp once. This siganls that the system is ready to accept programming.
4.Press and hold the selected transmitter button until alarm sounds a long chirp, indicating the signal has been stored into memory.
5.If you have additional transmitters, then repeat step 4 for each.
6.Flip the valet switch on then off.
7.The led will flash twice and the alarm will chirp 2 times. This signals that the system is ready to accept programming for receiver channel 2.
8.Press and hold the second button until the alarm sounds a long chirp, indicating the signal has been stored into memory.
9.Repeat step 8 for additional transmitters.
10.Flip valet switch on then off.
11.The led will falsh 3 times and alarm will chirp 3 times.
12.Press and hold third button until alarm sounds a long chirp.
13.Repeat step 12 fro additional transmitters.
14.Turn ignition key off. The alarm will sound one short chirp then one long chirp indicating the system has terminated the program mode.
This worked for me, I hope this helps.