When starting to yo-yo winding is probably the first thing you will learn. At first it is easiest to just wind the string around the yo-yo with your yo-hand whilst holding the yo-yo with your free-hand. With ball-bearing yo-yos you may need to place a finger of your free-hand over the gap of the yo-yo and loop the string once around the yo-yo to stop it from slipping as you try to wind it up.