Put on gloves, an N95 mask, and eye protection
Open windows and improve ventilation
Remove any wet items from the area
Vacuum the carpet with a HEPA vacuum
Mix warm water with a small amount of mild detergent
Lightly scrub the moldy area with a brush or cloth
Blot up moisture with clean towels
Apply white vinegar or a carpet-safe mold cleaner
Let the area sit briefly, then blot again
Rinse lightly with clean water and blot dry
Use fans and a dehumidifier to dry the carpet completely
Repeat cleaning if needed
Discard the carpet if mold has spread deeply or covers a large area