you can simply select 'email' in the social users list to allow users to sign up with email (and create temporary accounts).
There are options to integrate with Social Media like LinkedIn or Facebook, where you essentially set up an OAuth application that ties into FortiAuthenticator, so users can authenticate with their Facebook/LinkedIn/other account, but this is not what you're looking for, correct?
If you do want to go the OAuth route, you would have to create an OAuth server entry under Remote Servers in FortiAuthenticator, and an application entry in Facebook/LinkedIn/etc that FortiAuthenticator can then interact with.
+++ Divide by Cucumber Error. Please Reinstall Universe and Reboot +++