Creatures of Ava

First, you will need to acquire the Flute. You'll get the Flue as part of the main story. So if you're just starting out, simply keep progressing through the main story quests until you get it.

Once you've got it, you'll need to use it to shepherd 10 creatures at the same time. I was able to earn this pretty easily just north of the Arsira Village in this area here:



The creature called "Ura" is very common here (they look like a horse), and you only have to play 3 notes to get it to follow you: C > E > G.

If an Ura doesn't automatically follow you, that's ok! Press to stop playing your flute if you're currently playing it. Press to start playing it again, and the wheel with the various notes should appear. Play the notes mentioned above, and the Ura should join your group of creatures. In end, I was shepherding about 10-12 creatures with this method, and it looked like this (I gathered others in the area too, as you can tell):



There is a small section in the Databank under Tutorials called "Taming Creatures" that provides a bit information as well.