Do you know if your aftermarket alarm has a negative or a positive
lock pulse output? If it only has negative then you need to build a
relay module to operate your power door locks being that GM uses
positive power locks.

The lock module is located in the  relay centre on the passanger side
behind the dashboard. You will have to remove the lower plastic panel
below the glove box to access it.

I can give you colour codes but I need to reference my manual when I
get home.

Hope this helps.

Shane W.
1988 Olds 98 Touring Sedan