No mussels are needed; it does take a bit of muscle, but not much.

Feed the top of the bolt rope into the track and then place your hands (around the mast) on each side of the sail, just behind the track. Push your hands together (thereby sandwiching the sail between) and shove upward. Keep going until you hear the top hook. To take the sail down, push the sail up as far as it goes (to disengage the hook) and rotate the mast 60-90 degrees as you let the sail come back down past the hook. Gravity will do the rest, but you can slow the descent by keeping the mast slightly rotated.