Hit 'next' to get to the second screen, then select the 'a direct connection to my ISP using the following device' option, and choose the network adaptor you use to connect to your DSL or cable modem. Hit next.
Select 'yes' for Internet sharing to be enabled, and choose the network adaptor that connects to your home network. You will be prompted to create a startup disk to configure your client computers. You can skip this, as you have already done it. Hit 'no, do not create a home networking setup disk.'
Click 'finish.' That's all. Reboot.
Your gateway computer should have a new IP address of 192.168.0.1 and be giving out addresses in the 192.168.0.xxx range. Wait 5 minutes or so, or reboot the other systems in your network to test the connection sharing.
Hopefully you found this article useful in figuring out the mechanics of Internet sharing on your home network, and hopefully you learned something more about the networking of computers at the same time. Now that your home is fully set up for Internet access, it's time to sell the TV. :)