To use these light blue denim caps, simply place them on your head. They're great for daily wear, outdoor activities, or to add a stylish touch to your outfit. When it comes to maintenance, you can spot clean them with a mild detergent and a soft cloth. Avoid machine washing as it may damage the fabric. As for the warning, be aware that the product contains chemicals like cadmium, lead, and nickel which can be harmful. If you have any concerns, refer to www.P65Warnings.ca.gov for more information.