"engine" light, code P0505

The check engine light definitely has nothing to do with the cabin air filter. A DTC will have been logged by the engine ECU that will provide a hint about what is wrong.

The cabin air filter needs to be periodically replaced. Empty the contents of the lower glove compartment. Leave the glove compartment open and find the damper on the right side of the compartment. Pull one end of the damper off the pin that holds it in place.

Lower the glove compartment down.

Look at the portion of the ventilation system that can be seen. The filter is in a whitish plastic tray that can be pulled out. Remove the tray, replace the filter, raise the glove compartment back up, reinstall the damper, replace the contents of the glove compartment, and then you can close the glove compartment.