Edimax Technology QIG-ED-DB-0507-V11 - Manual (Page 8)

The thumb pushes out the bottom cover and turn over the cover and try to
re-assemble the cover in up-side-down direction. Then click the cover back to
position.
There you can see 2 plastic hooks, these hooks provide a fixed and flexible
grabs onto the steel frames of your ceiling (see the diagrams below).
QIG-ED-DB-0507-V1 8