Turn off the trimmer and turn it upside down, with the head pointing up.
Push down the bump button and then turn the spool counterclockwise to remove the spool from the head.
Remove any remaining string in the spool.
Bend the end of each piece of string and insert it into the eyelets on the center of the spool to secure the string in place.
Wrap the string around the spool counterclockwise.
Push each piece of string through the eyelets on the opposite sides of the spool, allowing approximately 6 inches of string to protrude.
Place the spool back onto the head and then rotate it clockwise to secure it.