To add or edit your location so it appears in your profile and under your Avatar:
(1) Near the top-right of any page, click "Settings." (1)
(2) At the left-center of the Settings page, click "Edit Profile." (2)
(3) In the "Location" box near the top of the page, add your location. (3)
(4) Important - At the bottom of the page, click "Save Changes." (Not Shown)
This is a browser method. I can't speak for Tapatalk.