2 ways: easy (sometimes), push end of string into hole on side until it appears out the bottom of the spool. Then push the end into the hole close to where it exited and pull it tight. Do the same on the other side of the spool. You should only havea about 15 feet of string for each side. Turn the ridged ring on the spool (inner spool ring looking at the bottom of the spool), counter clockwise while holding outer spool hoiusing (tension should be kept on strings during this process). If that doesn't work for you undo the bump button by unscrewing it counter clockwise as you hold th3e outer spool. Take the spool out of the housing and run the 15 foot string into the slot. It should appear out the bottom of the spool and ffeed the end into the nearby hole and pull it tight. Repeat the process on the other slot in the other section. Wind teh string clockwise I believe. It should say on thye spool if you look closely at the bottom. When you get the string wound, pull the string into onef of the notches on the top of the spool. Do likewise with the other string on the other side. Feed the strings through the two holes in the outer spool as you insert the spool into the outer housing. Replace the bump button. You should be reeady to go.