Hello I will help you with your question,
A scantool that can communicate with the RCDLR (remote control door lock receiver) must be used to place the RCDLR in programming mode. The best scantool is the Tech2, some aftermarket scanners may be able to do this but not all. Most well equipped shops will have a TECH@
Here are the service instructions that have to be followed to program the fobs
Transmitter Programming Important: All transmitters which are to be recognized by the remote control door lock receiver (RCDLR) must be programmed in a single programming sequence. If the system is placed in program mode it will erase all previously programmed transmitters upon the receipt of the programming signal from the first transmitter. Up to 4 transmitters can be programmed. Do not operate or program the transmitters in the vicinity of other vehicles that are in the keyless entry program mode. This prevents the programming of the transmitters to the incorrect vehicle.
Please let me know if you have futher questions about this