reprograming a keyless remote

i was wondering if anyone knew how to reprogram a keyless remote for a 2000 chevy silverado. i bought a knew one and want the old one to continue to work. if anyone can help i would appreciate it. thanks

There are 2 different ways to do it, I can't remember the year breakdown, If you do a search you can find them both, one will work the other won't
BTW, you will have to program them both at the same time.

you have to do all receivers at once. once reprogram mode is entered it erases all stored remotes
1 start with ingnition off, hold down the power unlock button on door panel. turn ignition key on,off,on,off, release power unlock button on the door panel. the locks will cycle once.

2 hold down the keyless entry transmitter lock and unlock buttons for 15 seconds. the locks will again cycle once.

3 repeat step 2 for each additional keyless entry transmitter.

4 turn ingnition on to exit the keyless entry transmitter proggramming mode.

check funtion of remotes

the second method requires scan tool