Using the 100% Altis Grey Mountain Bike Helmet is easy. First, choose the right size for you from XS/S, S/M, and L/XL. Put it on your head and adjust the fit until it's comfortable. You can adjust the visor as needed, which is also great for storing your 100% eyewear and goggles. When you're riding, make sure the helmet is securely in place. As for maintenance, clean it regularly with a mild soap and water. Don't use harsh chemicals as they might damage the helmet. Also, check the helmet for any signs of damage before each ride. If you notice cracks or other issues, it's time to replace it.