Username - the unique identifier of the user.
Username is a nickname which you can create by yourself according to certain requirements:
Your username must be written in Latin letters;
Your username must not be occupied by another user;
Minimum number of characters is at least five;
The use of numbers and underscore are allowed.
Step 1. Go to the menu "Settings"
Step 2: Click "Edit" button
Step 3. Click on the "username" field
Step 4: Create a username and click "Done"
Done! Your username is set.