To use this helmet, first measure your child's head circumference to make sure it's between 46 - 52cm. Then put the helmet on your child's head and use the EZ Fit system to adjust it until it fits securely. When your child is riding, always ensure the helmet is worn properly. As for maintenance, you can use a mild soap and water to clean the exterior and the padding of the helmet. Avoid using harsh chemicals as they might damage the helmet. Store the helmet in a cool, dry place away from direct sunlight. Remember to check the helmet regularly for any signs of damage, and replace it if there are any cracks or if it has been in a significant impact.