How to turn it off??

Wife's neon wouldn't start a few days ago during sub-zero temps.. However,
after unsuccessfully attempting to start car....alarm DID start..and now can't
figure out how to shut it off. Alarm will stop sounding after a few minutes,
but will start up again if she opens door. Tried locking/unlocking door, and
ignition switch, but no luck. What's the secret?

TIA