To breathe, one has to first gain the full breathe. Without gaining this, it is difficult to feel the diaphragm’s and ribs sensations.
To gain the full breathe involves straightening the spine, up to the throat. This requires several steps in posture changes, and may require some time.
After one has gained the full breathe, one’s sensations of the diaphragm will naturally tell one what to do, as breathing is mostly natural.
One can enhance still further with deliberate exercises.
To gain freedom in breathing, have to have lower chest support in front abdominal muscles and lower lumbar