scrub it off w soap
To clean mold or mildew from underneath a toilet's rim, you can use a commercial product like a mildew remover. You should spray the area with this product and wait about 10 minutes before removing the cleaner with a sponge. If the mildew is not completely removed, then repeat the process.
washing soft top with a mild bleach or water and vinegar will remove the mildew
Diluted bleach.
Rocks and sand
Mildew can be removed by mixing a 50/50 solution of white vinegar and water and spraying it on the mildew. Let the solution soak for a few minutes and then wipe clean.
dead matter,clean air, and water
Contact a company that encapsulates crawlspaces. You can clean tghe mildew but until you correct the problem, high humidity, it will keep coming back.
you can get good cleaners off amazon
Chlorine
Bit of spit and a rub
You don't...
put new vinyl on and be done with it.