Diagnosis
You don't need to remove the main cover for basic cleaning, which is risky. The real maintenance access is through the filter panels and rear grille.
How to Fix It
Unplug it. Remove the two side foam filters. Use a vacuum hose with a brush attachment on the exposed aluminum fins you can reach. For the rear condenser coil, use a soft brush or a vacuum through the rear grille. For deeper dust, use a can of coil cleaner (non-foaming) sprayed through the grilles, let sit, then rinse gently with a spray bottle of water from the outside.
If That Didn't Work
If the coil is moldy or heavily impacted, you need professional service. Disassembling the cabinet voids the warranty and can damage refrigerant lines.
Heads Up
Never use high-pressure water or a steam cleaner. You'll bend the delicate fins and possibly short electrical components. Gentle, external cleaning is all that's intended.