Here are the instructions from the service manual:
1. Turn ON the ignition, with the engine OFF, using a master Pass-Key® III key (black).
2. Observe the security telltale. After approximately 10 minutes the telltale will turn off.
3. Turn OFF the ignition, and wait 5 seconds.
4. Repeat step 1-3 two more times, for a total of 3 cycles or 30 minutes.

Here are instructions written from someone who has done many relearns.
1. Insert black key into ignition and turn to ON. Start 10 minute timer.
2. Wait for the yellow SECURITY light to go out and then turn the key to OFF for 5 seconds.
3. Again, turn igntion to ON. Start 10 minute timer.
4. Wait for the yellow SECURITY light to go out and then turn the key to OFF for 5 seconds.
5. Again, turn igntion to ON. Start 10 minute timer.
6. Wait for the yellow SECURITY light to go out and then turn the key to OFF for 5 seconds.
7. Again, turn igntion to ON and the car should start.

A couple points to mention. Roll the window down and keep all the doors shut during the entire process. Reach through the window opening to turn the key. If you have one, hook up a battery charger and charge it while you do the relearn. With the key on, it can drain the battery. To keep the load off the battery turn off the radio, blower fan and the headlights. Rotate the DELAY knob to OFF every cycle. Use a stopwatch or timer to keep track of the 10 minute intervals so you can stay on top of it.