The Gateway Control Console (sometimes referred to as ZNETMGR or Untangle) is a web based console where you can manage every aspect of network control, from content filtering to spam filtering, remote access to DHCP reservations, all in one simple web based interface.
You can find out the URL for the Gateway Control Console from the Commissioning Console, and below is a screenshot of the Commissioning Console, showing where you can find the link to the Gateway Control Console.
If you click on the link to the Gateway Control Console, you will be taken to the login page where you need to enter your Management user account username and password. (you will have to accept the certificate warning in your browser first)
Once you have logged in, you will be taken to the Gateway Control Console home page.