Gather these parts

Glue the pegs on the front of the hooks into the gaps in the bars of the vent.  make sure the hooks are pointed as show in the image. 

Move quickly to next step

Glue the back plate on so that hooks pass through the holes in the back.  If there is any wiggle room, try to make sure that the hook pieces are parallel. 

Flip it over and make sure everything is centered and glue the top ring on as shown