Twist the mounting bracket counterclockwise in your hands to separate it from the rest of the alarm.
Place the mounting bracket against the wall or ceiling where you will mount the alarm with the vertical mounting slot aligned in the 12 o'clock position. Trace marks through the mounting holes with the pencil.
Drill holes on each of the marks you made with the 5 mm drill bit.
Place the plastic screw anchors over the holes you have drilled and gently tap them in with a hammer.
Set the mounting bracket against where you have inserted the plastic screw anchors. Insert the screws through the holes on the mounting bracket and screw them in with the screwdriver.
Insert the 9-volt battery into the alarm.
Line up the guides on the alarm's base with the guides on the mounting bracket. Turn the base clockwise until the alarm snaps into place.