[Plugin: SEO Facebook Comment] Facebook App URL?

Whenever I try to add my URL in my facebook App to the App Domains, I get the following error:

Error
edgey.net must be derived from your Site URL or your Mobile Web URL.

Am I also supposed to have for the Hosting URL: https://ancient-tundra-1480.herokuapp.com/ ?

http://ww.wp.xz.cn/extend/plugins/seo-facebook-comments/