The easiest and most effective way to get rid of mold is to put a 50/50 mixture of bleach and water into a spray bottle. Then just spray the affected areas and let it sit for awhile. After it dissolves (if inside your home) you can wipe off with a rag.
I would use bleach and water solution, 10:1. Spray the drywall and allow it to dry, repeat the process several times to kill the mold. Do not soak the board
