After removal of both speaker grills they can be put into the new screen. Wait until the phone is fully reassembled to put the old grills into the new screen.

Align the two tabs of the grill with the two slots in the new screen

Carefully push the grill into the two slots. Start by pushing with your thumb and nail over one tab and only push one of the two tabs in at a time. A lot of pushing pressure is required so be careful not to damage the new screen.

If you are unable to push the grills in with your thumbs, try placing the grills in position and then pushing the screen face-down against a flat surface.

After one of the tabs is into the slot then the second tab can be pushed into the slot with some additional pressure. Both speaker grills can be replaced in this manner.

A couple people reported breaking their newly installed screen while popping in the speaker grill. Its also OK to not even install the cosmetic speaker grill.