How to upgrade estus flasks (not quantity)? (Dark Souls 3)

I need to burn something like bone or bone dust in Bonfire, I don't remember exactly.

And more precisely, someone will tell you, this question is also interesting.

It is necessary to burn a burning shard of bone in the fire temple in the main fire, and then the flask will become +1 then +2 and so on.
I found one shard of bone in the place where the giant figures with his giant arrows in the settlement of the undead, on the corpse that hangs from the ledge to it, you still need to jump.

morion2
Ok, got it. Thanks a lot. Just today I live in the Village of the Undead.