Possible locations for the cabin air filter include in the outside air intake, between the blower and the HVAC case, or over the blower at the back of the outside air intake. The owner's manual should indicate where the cabin air filter is located in that particular model.
Depending on the location, the cabin air filter is accessible from the glove box, under the hood or under the dash. The outside air intake is under the hood. The filter may be under a cover. If the filter isn't visible under the hood, searching around the glove box and under the dash is the next option.