Open the casement window fully with the hand crank. Once you have the window fully extended, you must be able to access the long lower pivot arm and the stabilizer arm.
Grab the outside edge of the casement window sash with one hand. Grab the pivot arm on the bottom of the casement window sash with your free hand.
Push outward slightly on the window sash, and pull the end of the pivot arm toward the keyhole slot on the bottom edge of the sash. Once the end of the pivot arm aligns with the keyhole, pull the arm down to release it from the casement window.
Repeat the process for the upper pivot arm, if your casement window uses a pivot arm at the top.