Setting an avatar and a nickname from the top navigation bar
Go to the right corner of the top navigation bar.
Click the user icon
.Select Edit user details.
Hover over user icon
.Click the plus icon
.In the Add/edit user picture popup click + Browse button.
In the File upload popup, select the picture that you would like to use as your avatar and click Open or double-click the picture.
Click Save.
Click
in the top right corner of the Add/edit user picture popup.
The selected avatar will appear instead of the user icon under Configuration > User details and in the right corner of the top navigation bar.
Other chat participants will see your avatar in a chat box next to your messages, if they enabled the Show avatars in chat window parameter under 
Chat configuration.
Note
You will not see your own avatar and nickname in a chat box.
Go to the right corner of the top navigation bar.
Click the
user icon.Select Edit user details.
Go to the Personal details section.
Fill in the Nickname text field.
Click Save at the bottom of the page.
As a result:
Your new nickname will be visible to other chat participants in a chat box next to your messages.