To clean a washable couch, you should first check the manufacturer's instructions for specific cleaning recommendations. In general, you can use a mild detergent and warm water to gently clean the fabric. It's important to avoid using harsh chemicals, bleach, or abrasive cleaning tools that can damage the material. After cleaning, you should rinse the fabric thoroughly and let it air dry. For more stubborn stains or odors, you can also use a fabric cleaner or hire a professional upholstery cleaning service.