To enable 2FA, as an Admin User navigate in WorkforceTNA to System Settings > General > Scroll to Authentication Settings.
Settings
Allow Users/Employees to login with Email Address: Allows users to login with email. With this disabled they need to use their username.
Enable Two Factor Authentication: Enables the use of 2FA for users.
Force Two Factor Authentication: Forces users to have 2FA setup on their account. If this is enabled after users have been created and logged in they will be forced to setup 2FA on next login.
If this is disabled users can skip 2FA on login.
Enable Remember Me on Two-Factor Authentication: Will allow the option to tick a remember me for 30 days on login. It will not request 2FA for 30 days on the same computer.