The air filter is located behind the glove compartment on the passenger side of the cabin. It's accessed by removing the lower trim panel beneath the dash.

The trim panel is held in place by two phillips head screws at the front of the panel. They're recessed in small holes that can be tough to see, so you may have to feel for them by hand.

Small tabs keep the trim panel in place at the front. Grip it by the sides, or by one of the small holes in the panel itself, and pull it down. You can pull it out of the passenger foot-well to get it out of the way.

Hidden behind the panel is the cabin air filter housing on the left, and the blower motor housing on the right. The air filter is hidden behind a plastic retainer, which is itself held in place by two sliding pieces of plastic (A and B in the image below.) Slide them towards the center, or out towards the edges of the retainer, to unlock it and pull it out.

With the retainer free of its housing, you can pull it down to remove it and the air filter along with it. Watch out for debris as it comes out! You'll probably have to vacuum the passenger footwell when you're done.

Well that was easy! Now you're working the same steps in reverse to install the new filter. Here's the old one and the new one, side by side. Despite their slight differences in shape, I found the new Mann filter (right) to fit just fine.

When you install the new filter, ensure the long flat edge is at the bottom, and the curved side is sitting flush with the curved vertical plastic tab on the retainer. This curved side of the filter will be facing away from you as you install it, with the 90 degree corner facing towards you. Install the filter along with the plastic retainer. Ensure the retainer is flush and fitted properly in the air filter housing.

Reinstall the plastic slide pieces to lock it in place. Once again, the plastic slide piece that's closer to you will probably be a pain to lock properly.

Reinstall the trim panel, starting from the back. Ensure the hook at the rear catches properly, and fit the tabs in the front in their respective slots. Take the two phillips head screws and reinstall them in the holes as before.