The only way to make a community private is by opting in to advanced features for your community. This is a decision made by the owner of the community when the community is created. Users may only submit public interviews to public communities and private interviews to private communities.
All other communities and their recordings are publicly viewable and searchable. The community will be visible to everyone publicly online (not just registered users of archive.storycorps.org). If your community is “moderated,” you have the ability to approve new members and approve interview submissions to your community page.