You need a router. It will sit between you ISP connection and your home network. Routers can supply a different IP address for each computer that is exclusively for an internal network, then route from those computers to the internet. A cheap router is normally sufficient for this. If you want WiFi too, then some more attention need to be paid to the quality of the WiFi access point that WiFi built into the router. As with most things, more money often get you equipment that is better in one way or another, but the difference may not be worth it to you.