1990 Buick Electra 1990 Buick Electra Park Ave keyless entr

It is not hard to do but I don't know the sequence for your car.
There is a series of turning the kye to on then off then on, etc that will put the computer (remote entry sensor/receiver) into receive mode. Your power locks will llikly cycle and you should now depress the button on your remote (with a good battery in it) to send a signal to your car. Now your car knows your remote and will be at your command.

This sequence with the ignition key should be in your owners manual if you have one or your local dealer should be willing to tell you how to do it.