The cabin air filter in your 2005 Nissan Altima is behind the glovebox. If you remove the glove box pins at the glove box door hinge, and then press the sides of the glove box toward the middle, the door comes off. Two tabs hold the filter cover on. Remove the filter cover and then pull the filter out.
When you install the new filter, make sure the arrow on the filter faces you and points up. There are two supporting tabs in the filter housing. Insert the new filter so the filter sits level on top of the tabs. Fill in the date on the replacement label that comes with the filter and put the label on the inside of the glove box door.
