Hey Tim, the easiest way I’ve found is as follows:
1. Mix soap and water in a bucket and put it in a garden sprayer or a trigger sprayer.
2. Spray the mixture on the underside of your awning — the part that’s not directly exposed to sunlight.
3. Roll up your awning and let it sit with the mixture for at least one hour to permeate the fabric.
4. Open your awning again and rinse it with water using a sprayer attachment on a hose.
5. Let your awning dry completely before closing it again.
This will work most of the time unless it is extremely dirty and/or has a lot of mold.
You can see the full details of each step here: https://camperfaqs.com/how-to-clean-rv-awnings