Your username is your email address. If you receive a notification about incorrect login details, log in with your bank credentials or mobile certificate via the "Forgot your user information?" section.
Please note that your username is different from your nickname, which appears in various games.
After this, you can create a new password and view your username from your profile.
Password requirements:
at least 12 characters
uppercase and lowercase letters as well as numbers
no references to personal or gaming account information