First attach the headjoint to the middle joint by inserting it and twisting both parts while pushing gently.
Use the same method to attach the foot joint to the middle joint. Line up the middle of the first lever on the foot joint with the end of the shaft on the middle joint.
The exact alignment of parts on the flute is a personal thing. The positions given here are useful as a guide, but you may wish to alter them slightly when you have been playing for a while.