Under: Admin Control Panel - Usergroups - Usergroup Manager
You need to Edit Usergroup "Unregistered / Not Logged In" and set Can View Forum to "No".
This may give you what you want as far as just showing a link to register. It will not hide everything though.
You can also surround any code with this to allow only members to see:
Code:
<vb:if condition="$show['member']"> ... </vb:if>