You can follow these steps to change your forum Profile name or your Avatar.
Assuming you've logged in the forum, tap your current profile icon. If your not logged in then tap 'Login Here'.
You can tap in one of three spots to continue the process: the 'Edit Profile' icon or in the drop-down menu Profile or Settings.
The login page will appear regardless if you're already logged in.
On the left of the page tap the SETTINGS button and the page will refresh to what you see here:
On this page you can change your forum User/Profile name and Avatar.
After submitting the change logout of the forum, close the browser, restart it and clear the cache and login back to the forum.
You should see the changes. If not repeat the above steps.