To dress a candle basically means to add extra stuff to your candle. You can add different ingredients. You can add oils and herbs and stones. Basically, it’s a way of dressing it up for a specific purpose. Think of it like you would when you dress up to go on a date. Your normal clothes typically will work fine depending on what you’re doing, but you can change the way that you dress to tailor your outfit to the specific event that you’re going to.