The default setting is that only links from within your web site will be allowed. To allow specific sites to have access to your content from links on their web page, you simply add their domains to the domain list.
The Unix version includes an admin form/script for adding/removing approved sites which are recorded in the domain list within your admin folder.
The Windows version is a different script and uses different functions. Approved domains need to be added to the statement in the top of the script itself.
In all cases, your own domain should be included in the approved list.