Relax into position vs force into position
Do not force the muscles into a “correct” position. A correct position is in fact a skill of effortlessly forming the lips in a relaxed, coordinated way. Forcing the embouchure to «look good» will cause unnecessary (and potentially harmful) tension in the jaw.
Activating the correct muscles might get frustrating. Have patience and experiment, also away from the instrument. Use a mirror.
Trying to shape lips according to a description might cause excessive tension in the jaw and other muscles.
Good position of lips, chin and jaw is relaxed. You can think about “Relaxing into position”. Do not wrestle with the embouchure.
Methods
Alexander technique: silent AH