Disable the cage lock and decompress the clutch spring by rotating the cage counter-clockwise

Unscrew the derailleur cage bolt. After that the cage can be removed

Unscrew the cage bolts as shown on the picture below

Install the derailleur pulleys

Tighten the derailleur pulleys and cage bolts

Turn the cage clockwise by 1 turn and enable the cage lock

Tighten the cage set bolt (lower picture is applicable for 12-speed derailleurs, upper one for 11-speed derailleurs)