Three wires, power(red), ground(black), and remote(yellow).
Connect the red and black wires, and connect your yellow wire to your alarm units "+" signal wire when armed (one of your alarms accsories wires). The alarm unit should have two wires for acc when armed, you have a "-" and "+" wire for accsories only when the unit arms. So find this wire and you're set.
You would need the wiring diagram for the alarm unit to find this wire easier.
I have one of these too, so hope this helps you out.