I work at an Italian restaurant and my boss gives great advice. I can ask him how to cook anything.
This is incredibly simple
Cut bread into cubes or chunks. Toast on 350 for 10; or until toasted. Melt half a stick of butter (1/2 cup) in a saucepan and sautee diced onions and celery ’til tender. Throw in bread with some chicken (or Turkey) stock (gauge off of how much bread crumbs you have. You don’t want mush) and your favorite seasonings. That’s it. I’ll throw mine in the oven to crunch it up too (I stuff my bird with whole onions and apples.