Hi Doris - welcome to the site
It is as Gambit says behind the glove box draw, open the draw to its fullest and you can see there is a small retaining bar on the left side - this will just pull off allowing the draw to drop slightly more, it will now be stopped by a plastic post on both sides, there is enough flex in the draw to pull them in wards and allow the draw to drop further its a bit tricky to get them both in and allow the draw to drop all the way. When all the way down the draw will pull away from its hinge at the bottom.
The filter is now right in front of you and reminded me of looking at a video cassette, just pull the existing filter out and replace with the new.
If you are still stuck I can get some photos tomorrow.