This is a pic I lifted off their website: http://www.dactyltech.co.za/vansecurity.html
I did a very similar thing on my windows. The windows are easier that the doors because you don’t get that thick rubber surround on the windows that you get around the door, you just screw that little box onto the window frame and stick the magnet to the window with mounting tape.
If you want to leave windows open at night you can just disarm that circuit and leave the side tent and door circuit armed – nobody is going to get in through any window without waking you up, so you can gang all the windows onto a single circuit.