Hello there,
Please mention the name of the examination which you are enquiring about. Then we can provide you the helpline number and their email.
Or you can try finding the username in your registered email. They must have sent you the credentials during the verification process. Go through all the messages. Check the spam folders too.
Once you find your username, you can change your password by clicking the 'forgot password' option. You should preserve the credentials properly.
Hope this answer helps you.
Thank you!!