How do you clean the filter

In order to look up the filter change procedure I would need the specific model number. However, filter changes or washing should be done regularly. Look for a very simple lift-out design that is washable in the kitchen or laundry sink. Soak in soapy water and rinse with spray nozzle.

As for the symptom "Blows out warm air" this is expected. The dehumidifier is less than 100% efficient, meaning that the energy that is used produces heat in the exhaust air. A 100% efficient design would still send all the heat energy of condensation (endothermic phase change) into the exhaust air. You should expect 1072 BTU per pint (1 pound of water). This is far more than the heat of crystallization (144 BTU per pound of ice) and therefore much more sensible when you feel the discharge air from the dehumidifier. Dehumidifiers typically operate in basements to both warm and dry the area where a sump pump may be operating to remove the water that seeps through the foundation. A dehumidifier is not a good idea for warm areas of the house. This will decrease the efficiency by increasing the temperature differential needed to get the evaporator coil below the dew point to cause condensation. The condenser coil will be much hotter than expected if the unit is operated in a warm humid room. Only air conditioners which discharge condensate and exhaust air to the outside of the structure should be used to cool a room.