Hello there,
It seems you have missed out certain details. You haven't mentioned the name of the examination. But don't worry, we are here to help you out. Check the inbox of your registered email id. The authorities might have sent you the credentials during the verification process. Check the spam folders too. Also check the messages in your registered mobile number. If you still cannot find it, you can write an email to the authorities about your problem.

Once you recover your username, you can easily change your password by clicking the"forgot password" option.

Hope this answer helps you.
Good luck!!