Read the following carefully and follow/click and read the links (in blue) in the articles.

• https://support.mozilla.org/en-US/kb/block-and-unblock-websites-with-parental-controls
• http://kb.mozillazine.org/Parental_controls

If you are looking for complete parental control that records everything teens do online (such as Facebook) , as well as filters inappropriate websites, and does linguistic analysis to watch out for dangerous behavior - such as online predators or cyber bullys - check out McGruff SafeGuard's Parental Control software