1995 Buick Riviera: Reprogramming remote keyless entry

The batteries in my remote keyless entry transmitter for my 1995 Buick Riviera recently died. Although I replaced them with new batteries (which I know are good), the remote keyless entry system no longer works. Can someone explain to me the procedure for reprogramming a remote keyless entry for a 1995 Buick Riviera?

The batteries in my remote keyless entry transmitter for my 1995 Buick Riviera recently died. Although I replaced them with new batteries (which I know are good), the remote keyless entry system no longer works. Can someone explain to me the procedure for reprogramming a remote keyless entry for a 1995 Buick Riviera?
try holding down lock and unlock for 6 seconds