How do I replace the Odor & VOC Reducing Pre-filter?

Remove the rear grille by pressing down on the tab and pulling it toward you, then gently untuck the old pre-filter from the plastic retention clips and dispose of it. Place a fresh K Pre-filter (Model HRF-K2) onto the rear grille, tuck the edges under the plastic clips to hold it securely, and reattach the rear grille to the air cleaner. (Page 4)