Two-factor authentication creates an additional step to the login process where you will be requested to provide a one-time passcode to access the portal or Management Console (this is dependent on your portal settings).
Once you have either successful entered your credentials into the portal or you have clicked on the Management Console, you will be presented with the one-time passcode screen.
Select GET OTP, you will now receive an email to your registered email address with a 6 digit one-time passcode.
The 6 digit one-time passcode will only be valid for a limited time, and should be entered into the on-time passcode screen and select VALIDATE OTP.
If you experience any issues login in with One-Time passcode please check out this article of One-time passcode is incorrect.