Keyfob Programming?

I have a 2000 GLS. It normally comes standard with a keyfob. but I have bought the car used and there wasnt a keyfob, but only dealer copies of the keys.

I have a few GM keyfobs that might be able to be programmed to the car.

Ok my question is How do I get my Alero into programming mode? And once I get it into that mode what do I have to do to the Keyfob so my Car recognizes the signal?

I stress the first part of the question alittle more than the second. And I dont want to go to a dealer and pay money for this, as it is only a convenience issue not a nessecity.

Any help woul dbe appreciated. Thank you all very much.

-Chris