Hey Tim, I always recommend consulting the owner’s manual to see what specific instructions the manufacturer has for their filter and to determine whether it’s a one-time-use or washable filter. If you can’t find your owner’s manual, you can usually search for it on Bing.
That said, if it is a washable filter, you would typically just remove the vent cover from your AC unit, remove the filter, and vacuum it clean, being careful not to damage it.
If it is extremely dirty, which yours might be, follow the instructions here: https://camperfaqs.com/how-to-clean-rv-air-conditioner-filter