Turn off the weed wacker and remove the battery or disconnect the spark plug
Wear gloves and safety glasses
Open the trimmer head
Remove the old spool or remaining string
Cut the new trimmer line to the correct length
Insert the line into the spool or head
Wind the line evenly in the direction indicated on the spool
Leave equal lengths of line on both sides
Thread the ends through the eyelets or exit holes
Reassemble the trimmer head
Pull the line out slightly if needed
Test the weed wacker at low speed