Step 1: The Sensor
The white arrow points on the actual magnetic sensor, this is where you want to attach your microswitch.
On the third picture you can see the delay controller and in order to have the sensor send a signal without a delay you need to short the 4 marked points to the upper right in the picture. See picture 4.
Step 2: Microswitch and Mounting
As you can see I was able to put the whole thing in my door lock, however once the door was closed the signal couldn't be reached, so I had to attach an antenna, and I just guessed and attached a wire to point marked in yellow. The antenna is then routed to the inside of my apartment as you can see in the last picture.