This base layer is designed for straightforward use. Simply pull it on as the first layer of clothing. It's designed to be a regular fit and is true to size, so selecting the child's usual clothing size should provide an optimal fit. It is compatible with all athletic activities, particularly those requiring sustained physical effort where temperature regulation and muscle support are beneficial. For care, this base layer is machine washable according to the care label instructions. Always remember to keep it away from fire to maintain its integrity and for safety.