In the Fresh theme there's an option in the theme settings to show/hide the Login/Join buttons. You as administrator can just navigate directly to the admin pages and you'll be asked to log in.

Also you can set the Membership Policy under Users & Permissions to what is appropriate for your site. If you don't want people to be able to join then ensure it's set to Private.

Thanks

Joe

Thanks Joe, I didn't fully understand the implications of making it 'Private'. I now see that the 'public' can still see all the necessary pages without 'Logging in'.