2001 keyless entry

Good morning every one:

I'm new and confused. I own a 2001 GMC 2500 truck and bought a used keless entry transmitter as a back up to the one I own now. I would like to know how to program this used keyless entry to my truck. I'm a mechanic and I just cant see my self paying a mechanic for something I can do my self.

2001 GMC Heavy Duty 2500 Crew Cab 4X4
Rod
Calgary Alberta

you gotta press and hold lock + unlock for about 7 seconds you will then hear the doors lock

When You Program The Remote, You Have To Be Near The Truck With The Doors Unlocked And The Drivers Door Open........where Can I Find The Remotes New For Purchase?
Kevin