programming key fob '99 Durango

My son just bought a '99 Durango from a local used car lot. They gave
him 1 key fob but it doesn't work. They told him it was probably dead
batteries. He replaced the batteries and it's still not working.

As a young guy he did not add it to the list of what should be
corrected as part of the sale. He also didn't get the owners manual.

Could someone tell me how to program the key fob for the Durango? I've
been searching the net and haven't found anything specific to the '99.

Thanks!

Jim