Instructions
Twist the unknotted end of the string. The string is folded at this end and twisted together. The string will untwist and form an open loop.
Slip the loop over the side of the yo-yo so that the string goes between the two sides and retightens itself. Fold the other end of the string, the end of the string with the loop, at the knot. Pull the string through the loop to forming an adjustable loop. Slip this loop over your finger.
Hang the yo-yo from your finger to straighten the string. Pick up the yo-yo and wind the string around it. If the string twists as you wind it, the string is too tight. Let the yo-yo hang. Spin it to the right a few times to tighten the string.
Wind the string around the yo-yo again and "yo-yo" a few times. If your string is twisting up as you yo-yo, the string is too loose. Drop the yo-yo and spin it to the left to loosen the string.