The vent grill kept falling off because plastic tabs had broken off.

I got my 5 foot step-ladder and Phillips screw driver and removed two screws that were already there. I discarded the two metal clips because new metal clips are already inserted in the vent grill. I lined-up the vent grill on the microwave and screwed in the two screws. It's a perfect fit.

I'm a 62 year old woman, and if I can do it - anyone can. The vent grill arrived two days after I ordered it.