1- For finding Facebook avatar at first you should be sure your Facebook is up to date. for that go to the App store and write Facebook in the search bar and be sure that your app is up to date.
2- Open your Facebook app.
3- Click on the Settings, at the top right corner of the screen.
4- Click on “See More”.
5- Click on Avatar.
6- Here you can create your desired avatar, also you can click on the mirror and after that, the camera of your cellphone will be turned on and you can see your face near your avatar and you can create your avatar easier.
7- You can specify eye and eyebrow shape here.
8- Specify Nose and mouth shape here.
9- Specify the body shape and other characteristics of your avatar too.
10- Click on the approve key, at the top right corner of the screen.
11- Follow these steps to finish your job. now you have your avatar in the Facebook application.
If You want to know how to post or share or edit your facebook avatar you can follow the above links.