Disconnect the spark plug wire or remove the battery
Wear gloves and safety glasses
Remove the trimmer head cover or spool cap
Take out the spool from the head
Remove any remaining old line
Cut the new trimmer line to the correct length
Insert the line into the spool holes or slots
Wind the line evenly in the direction shown on the spool
Leave the required amount of line ends exposed
Thread the line ends through the head eyelets if needed
Reinstall the spool into the trimmer head
Replace the cover or spool cap
Pull the line ends to confirm they feed properly
Reconnect the spark plug wire or reinstall the battery
Test the trimmer at low speed first