Set the trimmer on a flat workbench. Slide the ignition switch to the OFF position. Turn the trimmer over so that the cutting head is facing up.
Push the two tabs on the side of the cutting head; pull the spool up and it will slide out. Cut approximately 20 feet of trimmer line. Place the new trimmer line into the two eyelets on the spool, wind the line clockwise until there are 6 inches of line remaining. Install the new spool so that the line and the slots align with the eyelets in the string head. Thread the line into the eyelets.
Pull the line extending from the trimmer head so the string will release from the slots into the spool. Slide the spool back onto the trimmer head until the tabs click into position.