remote start on 98 tahoe?

i just got a tahoe its got a alarm and i was told it had remote start and im not sure how to opperate it. it has 4 keys 1 lock 2 unlck 3 panic and the other does nothing do i have to hold 2 of them or is it just one?

try holding the 1 and 2 button down at the same time for 2 to 3 seconds then let go.

the lock and unlock or the 2 bottom smaller buttons?