Here is a link for a handy little track sheet: https://www.bavauto.com/Assets/inst_pages/e36mc.pdf
I chose a MANN filter. There are others available. I'm on the fence about aftermarket air filters given the increase surface area means little with the stock throttle body and manifold. Perhaps when I upgrade those, it might be worth considering. For now, a clean filter is better than a dirty one.
Drop in your new filter.
Slide the tray back in. Snapping the clips in place.
Now enjoy driving with a fresh filter.