Set the feet of the ladder against a stair (or better yet a wall), making sure the feet are even and flat against the ground. Make sure it is not too vertical. And the top goes against the opposite wall. *DO NOT TAKE THIS AS EXPERT ADVISE. TAKE PROPER PRECAUTIONS WHEN YOU USE A LADDER*
I sprayed this mixture of one part bleach to three parts water on the mildew and let it sit 10 minutes before wiping it of with water.