In order to connect a Facebook Group to your StoryChief account, we'll need to authenticate through your personal Facebook Profile that has "Admin" role on the Group you're looking to connect. It is not possible to connect Groups that you are only a member of. More information on Facebook Page Roles can be found here.
Facebook groups owned by pages
Facebook now support the creation of Groups from Pages. If you're looking to connect a Group that is owned by a Page, you'll need to make sure that your personal Facebook Profile is set up as an Admin.
If you go to your group first make sure you are "acting" as the Fanpage. Then you can make your personal profile admin