How do you speak from your diaphragm?

Answer 1

Have a look at the page below - it's about breathing and using your diaphragm.

Answer 2

You can learn how by lying on your back and taking a large breath and watching to see if your belly rises as you take the breath. Breathing from the diaphragm uses lower back muscles as well as belly muscles. Push the air out as you vocalize (aaaah) for increasing amounts of time. The expected length of vocalization is 25 to 30 seconds. Practice lying down at first, then standing or sitting. This will teach you to breathe from your diaphragm.