How do you program a NEW remote transmitter?

I got mad last night and launched my keys across the room, now my remote transmitter for my 1999 Alero does not work. I take pictures of cars for a living and was able to get a new remote transmitter that is for GM and looks identical to my original. I am wondering how do I program it to get it to work? If that is not possible how do I get my old one working again? :confused::confused:

Thanks!

Transmitters may look alike, but they are not.....they have to look alike AND have the same part number on the back......more often than not, the newer fobs have to be programmed by a dealership.....

Transmitters may look alike, but they are not.....they have to look alike AND have the same part number on the back......more often than not, the newer fobs have to be programmed by a dealership.....

that better be free then