This could either be done by adding to the Further Reading section or by adding text to the FAQ body.
FAQ 23
If you would like to control who can read your journal entries, see
http://www.livejournal.com/support/faqbrowse.bml?faqid=24
FAQ 24
CONTROLLING COMMENTS
If you would like to control who can post comments on your journal entries, see
http://www.livejournal.com/support/faqbrowse.bml?faqid=23