Secure zones are areas in your site that require a log in to access. You can add secure zones to your page simply by selecting one.
Where can you find Secure Zones?
From your Page Details, scroll down to the bottom, beneath Open Graph Settings.
This option will only be available if you have created secure zones.
Within Secure Zones, you can add a Secure Zone to your page, such as 'My Account', ensuring that to see this page, you have to be logged in.