It took me years to discover, if you tug on opposite corners, the center of the model expands into the body.

You may need to curl the wings a bit, but they will flap.

Hold the crane by the chest with one hand, and pull on the tail with the other hand.

All the folds are complete.

Adjust the angle of the head, and flatten the neck back down.

Open the neck a little bit, and push the head down between the layers of paper.

Crease well, and unfold.

Valley fold the head.

Flatten the bulge in the tail of the crane.

Extract the tail, allowing a bulge.