bmw z3 alarm assistance ed

Hi. I just joined and I need guidance. I have a 1996 BMW Z3 that I have alreay installed the alarm. The system has a shock sensor that works fine, the remote turns the alarm on and off via the 2-way remote. This is where it gets difficult. I would like to have the alarm activate the car horn, lock and unlock the car (the car harness has the cables and the alarm is set up to do it) roll up the windows when locked. I have the module already. My questions: (a) how does the possitive trigger work on the car locks? (b) I have located the cables going to the center console for each window and need to know which cable to cut and how to install the roll up module (c) the car has already a cable that activates the horn from the harness, but I need to add a relay. Your assistance is appreciated!

For a: I found the following diagram on how to use a relay to change polarity: 

https://www.the12volt.com/relays/page1.asp#p2n

For b: what is an easy way to test the polarity of the trigger?

For c: you are correct, the alarm only puts out 3mA hence I will use that output to trigger a relay to provide the horn with enough current to operate.

Thank you for the assistance!

They are positive in this model, it's based on the equivalent 3 series and the control unit is behind the glovebox centre quad-plug, pin 4 lock and extend lock pulse to 8secs for window close,  pin 17 oposite 4 is unlock. Right hand plug has 3 wires, BROWN / blue? and BROWN / grey? with silver or yellow dots (can't remember everything! )  But they are the only 2 on that plug with either silver or yellow dots, these are the door contacts -going diode them together, third wire is BROWN / white, trunk - going. No need to worry about sleeper circuits on this car, 12v+, RED / blue, Ign = light green, Starter = GREEN/ black (which changes somewhere to black yellow) 2nd. ign NOT acc is purple. All on loom from ign switch.

You can also deadlock by using a second aux , set it for 2secs, flip it (relay or power transistor, it's only about 100mamp)) to pos. and diode out to lock and unlock. Thus you can have lock and close, autolock  on ign without deadlock and arming with deadlock.

PS I diode block the lock outputs from the alarm, I've had issues otherwise with current DEI product that doesn't have relay driven locking e.g. Clifford Concept series.

There the BMW master strikes again and I've only ever done one of these about 18 months ago!