You can change your screen name any time you want, provided the new name you want is not already in use.
Access Profile Page
Select the Profile menu selection in the header, to take you to the Profile screen.

Select button: Change/Set Screen Name

Enter your desired screen name
Enter your desired screen name in the input field, and hit TAB to leave the field. That last part matters.
You’ll be informed if the desired screen name is or is not available.

If it’s available, select: Save

And that’s it
