To turn on or manage two-factor authentication:
Go to your Security and Login Settings.
Scroll down to Use two-factor authentication and click Edit.
Choose the security method you want to add and follow the on-screen instructions.
When you set up two-factor authentication on Facebook, you’ll be asked to choose one of two security methods:
You'll need to have at least one of these set up in order to use two-factor authentication. Once you have added either text message (SMS) codes or a third party authentication app on your account, you'll also be able to set up some of the optional methods below: