How to use the firewall to deny access

Hello Community

    On a Windows 2008 Server running an intranet, the site
is accessible by type the http://ServerName:PortNumber into the address bar.

    How can I setup the firewall on the Windows 2008 Server so that
when a user types the http://ServerName:PortNumber into the address bar
they are denied access to the site? 

    Thank you
    Shabeaut