How do I block inappropriate websites in Parental Controls?

Hi,

 

First of all, I want to thank this forum for the answers I have been able to find using the search button.

 

I can't seem to find anything on how to block inappropriate websites in Parental Controls using XP or vista.  I thought there would be an input screen or when I see a site in the browser history that I want blockes I could 'press a button' or something to block it.  What am I missing?

 

Thanks in advance.  I'm using Norton internet security 2009, xp and vista, internet explorer 7 and firefox.