This is a project that demonstrates logging in with facebook or google using the UE4 OpenID Client
Note: This example requires you to use the plugin bought from the marketplace!
For Facebook use the following user to login (if you're using the default app provided in the example):
user: open_miywmve_user@tfbnw.net
password: 1qazXSW@3edc
Using the above account won't promt the dialog for "allowing / disallowing the app certain permissions" because they are already allowed. If you wish to properly test this, make your own facebook app and test users as shown in the video tutorial.