Stand in front of a mirror. Watch your Adam's apple. Yawn. Yawn and sing. Take note of the muscles that moved your Adam's apple down.
Speak with a voice like the cartoon character Yogi Bear. Take note of the muscles that activate in your throat to make that sound. That is the sound of a lowered larynx.
When you are aware that your larynx is rising, activate those muscles we just identified, and use them to bring the larynx down to a more neutral position.
Become aware, by watching in a mirror, of when your larynx rises. Learn to compensate for that by bringing it down to the neutral position.