To install or replaced the Anti-Allergy Enzyme Filter, you will first need to remove the primary air filter. To do this, turn your unit off then open the front panel. Push up and back on the primary filter until the two tabs holding it in place are exposed. You can now slide the primary filter out of the unit. On the back of the primary filter, you will see a rectangular opening the same size and shape as the enzyme filter. Simply snap the filter in the opening, and then slide the primary filter back into the indoor unit. Make sure the tabs on the filter frame are in the appropriate slots before closing the front panel. You're now ready to turn the unit back on and enjoy clean, healthy air.