With the shade removed, remove the equalizer assembly from the pull cords. Slide the cord lock off the headrail assembly, pulling it free from the pull cords. Leave plenty of extra cord length hanging free. With the shade reinstalled in your window, adjust shade level by reattaching the cord equalizer. With the shade removed and in the stacked position, remove plastic end caps and cord locks from the top and bottom rails.
Slide rails off the pleated fabric.
Note proper path. Install new string in exact reverse and secure at bottom rail. A large needle can be used to feed the string through the fabric. Do not adjust the cord length yet. Reassemble the shade, then reinstall I window where proper rail level can be determined.