Scrub off what you can see with a brush, soap and water. Then spray it all down with Clorox. You can then treat with a commercial mold prevention solution, some of them can really retard regrowth.

only takes the stain away, but if you bleach it while the spores are still alive, they will just multiply because the spores get warmer with bleach, and thus sexually stimulated.

I used any detergent I had, usually dish soap.

Note the past tense: I live in the desert and no longer have to shave the mildew off the furniture once a week in summer like I did in coastal New England.

Install soffit vents or roof or ridge vent or open the doors during part of the day.

You can scrub it with bleach, which is good, but it will come back. All you need is air flow from bottom up, and it's not a big deal. It's good you caught it early.

Use according to instructions. Kills the surface algea here I Houston.