You want to wipe down the walls with a brush or a towel to get rid of the visible mold first. Now rinse the brush or if using a towel, get a new one so you can clean the remaining area. Use a mix of bleach, water and detergent, as long as walls are not porous. If the wall is porous, do not use soap and water. Be sure you have your windows open for ventilation and dry the area immediately after.