I get this error message when trying to authenticate

I get this error message when trying to authenticate from with the widget: - "Given URL is not allowed by the Application configuration.: One or more of the given URLs is not allowed by the App's settings. It must match the Website URL or Canvas URL, or the domain must be a subdomain of one of the App's domains."

Can you tell me what the config settings within the app should be so that this works? What am I missing?

Thanks!