I have a Hisense dehumidifier DJ6A4JF0508 and need to clean my filter plz tell me how

It appears to be a Humidity Sensor error.

https://www.google.com/search?q=HiSense+30+Dehumidifier+F-9+error

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Contact Hisense directly to request the diagram. Be sure to identify model.

what did yo do with the manual?

dirty or clogged filter coil --fan failing --low freon

Here's a link to an article written by a service technician with more than 30 years of experience. It gives details on How to Clean Dehumidifier

PLZ try this link for ur support:
http://homeappliance.manualsonline.com/support/maytag/dehumidifier/instruction-manual-3294618

How often does the unit run? Does the fan run when the unit is suppose to be running(as the fan pulls the air thru the filter). If every thing operates correctly and the filter is in the right location on the unit then all I can say is that you keep a clean house. Personally I only need to clean the air filter on my dehumidifier about once a summer. I wouldn't be overly concerned if it isn't getting very dirty.

This will need to be serviced. LG has a 5 year warranty on these models. They usually will tell you of a service center nearby which will service it free of charge since it is under warranty. If you do not live near a service center they may ship you a replacement and you send your old dehumidifier back to them. Make sure you have your reciept when you contact them so they can verify it is 2 years old.