Honda locates the cabin air filter behind the glove box. While I haven't changed my Passports yet as it has 1100 miles on the clock, I have change many others. It takes about 5 minutes to empty the glove box, squeeze the sides to release it and drop it town. Now the air filter is visible and can be removed and replaced. Simple job and a new filter is about $10.
I change mine annually. When we get forest fires in NW Montana, they get dirty pretty fast.
Mike