Log in to the my.ryerson portal with your my.ryerson user name and password.
Under the 'Self Service' module, click on Personal Account.
Under 'Security' section click on Two-Factor Authentication.
Under 'Two-Factor authentication is set up for' field you will see Revoke for the Mobile device option. You may want to revoke your device if you have either lost or replaced your mobile device or if you no longer wish to use Two-Factor Authentication.