You will first also need to know how to create an app..
Please see this /easywebinar/chat-option-settings/facebook-app-how-to-make-one
After you have created your FB app you can paste in your App/api key as seen below into your automated event.
Keep in mind that this is just a comments plugin and these comment do not get seen within anywhere inside facebook, These comments will also not reset for the next event. They will continue to grow and be timestamped.