reset car alarm for 2004 subaru wrx after we disconnected the battery?

we disconnected the battery to replace a headlight bulb, when we reconnected alarm went off. tried to use emergency overide without transmitter as bought car used without it, wouldnt start, got it to start but went off again when shut off car. disconnected battery again, and finally started to get it home but when try to start the alarm goes off and wont reset. Please, any help would be great.