Hi Amy I'm going to answer in the support email we have going, but just in case anyone else had a similar question....go to your Settings, under Basics, and choose "Private" rather than "Public." That will put the entire community behind a login, so that "guests" or "visitors" can't see anything without registering.
If you want to prevent new registrations, or limit to invitation-only, you can also go in Settings, to Registration Settings, and tick the box to restrict those options as well.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .