how can i program the computer

The parts supplier, Jeep dealer and a 'few' auto repair facility's have the capability ... Not doable or.

as pushrod stated>>1999 Jeep Grand Cherokee 2WD/4WD: Flash technology. OEM #56041423. **Requires factory reprogramming/programming**. This is a flash unit..

You may need to replace it with a pre-programmed one, or send yours off for programming. Dealerships are often the only local resource for most people. Car computer Exchange is a company that many of us have used. https://carcomputerexchange.com/