Turn off the weed wacker and disconnect the spark plug or remove the battery
Wear gloves
Lay the trimmer on a flat surface
Remove the trimmer head cover or spool cap
Take out the old spool or remaining string
Cut a new length of trimmer line to the correct size
Thread the line through the spool or eyelets as directed by the model
Wind the string tightly and evenly onto the spool
Leave the required amount of line exposed
Reinstall the spool into the trimmer head
Replace the cover or cap securely
Reconnect the spark plug or reinstall the battery
Test the trimmer briefly to confirm proper feeding