1. Login to your account at https://accounts.theorycraftgames.com/

2. Click on the Account Profile tab.

3. If you want to change your username, input your preferred username on the field. Do make sure to delete your original username first.

4. If you want to change your display name, do the same steps but instead of the username, look for the field under "Display Name". 

5. Click on "Save Changes". After that, you're done!