Facebook Link Problem - Can Anyone Help Please.

When I try to link my FineArt account with my Facebook page by clicking on the 'enable' button, I get the following error message:

Given URL is not permitted 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 anyone tell me what this actually means please?

Thanks
Sue