How can I replace a line in a Ryobi trimmer head?

To replace a line in a Ryobi trimmer head, first, remove the spool from the trimmer head. Then, unwind any remaining line and clean the spool. Cut a new piece of trimmer line to the appropriate length and insert it into the spool, following the arrows for the correct winding direction. Finally, reassemble the spool back into the trimmer head.