This short video walks through the steps required to configure the Facebook Feed web part:
Requirements and Activation
Please make sure the following URLs are accessible on your SharePoint WFE and App servers. These are service URLs that power the Facebook Feed web part functionality. If these are not accessible, then the Facebook Feed web part will not work.
To activate the Facebook Feed web part on your site collection (this has most likely already been done) navigate to Site settings > Site collection features and choose to Activate the "Emgage | Facebook Feed Web Part."