In Moodle, how do we direct people to hidden sites?

Please answer this if you can, and then retag it. Thanks

To clarify the question, if we make the site “not available to students” then it’s not going to show up on the list of available sites, or sites that can be enrolled in. Is there any way to let the people we want subscribe to it know where it is? (Give URL with Enrolment key?)