By enabling two-factor authentication on your account you will be required to provide a 6-digit code in addition to your username and password when signing into the system. This code will be sent to your registered email or via SMS to your phone number.
To enable two-factor authentication, navigate to your profile page if you need to add phone number - or directly to Security if you just want to enable the two-factor authentication right away:
Follow the link to "Security " in the menu. If you wish to use two-factor authentication by receiving verification code through SMS, you must have first registered your phone number as seen in the photo below:
On this page you should see the option to enable two-factor authentication:
Once you have enabled two-factor authentication you will be asked to provide an authentication code every time you sign into the system. Once you have successfully signed in with your username and password, you will be asked to choose a delivery method for the authentication code. If no phone number if registered on your profile you will only be able to choose email, if you have configured your number the system will automatically use SMS.
This is what you see if you haven't added the phone number:
If you have added your phone number it will look like this:
If you wish to disable two-factor authentication, you can do this on the edit profile
under the "Security" tab.