To use this long sleeve thermal base layer, simply put it on like any other shirt. It's perfect to wear under your regular clothes during cold days or as a base layer for physical activities. When it comes to washing, use a gentle cycle with mild detergent. Avoid using bleach as it may damage the fabric and the anti-bacterial treatment. After washing, let it air dry to maintain its shape and performance. You can wear it every day as it's so comfortable, but make sure to follow these care instructions to keep it in great condition for a long time.