How to fit Ring Alarm Door Sensor with door that isn’t flat

I have a new door fitted to my house. I just bought the Ring Alarm. I am trying to fit a door sensor. However, not only does the door not sit flush with the frame, it has an additional section that is angled making it hard to fit the sensor. Quite hard to explain, I have attached an image. You can see firstly the door isn't flush. But even if it was, there is a large gap between the part of the door and the part of the frame I would attach the sensor too. Any ideas?