Use the double side adhesive tape to fix the main unit at the side of the door/window.
Attach the bar magnet to door frame/window frame with the arrow aligning with the reference line of the main unit
Test the setup by switching the system's switch to 'ON' position of the main unit and see whether the alarm can be triggered by opening the door/ window.
1 x Window/door entry alarm
3 x 1.5v/LR44 Cell Batteries
Size: 150*90*25 mm