If you want to use the computer on the Internet independently of each other, you don't have the right equipment. You will need a router. If you want shared access via one computer, you can use windows ICS (Internet connection Sharing). I don't recommend ICS, but you can google how to set it up as I've never did this before, but know people that have succesfully used it.
If you puchase a router, you should have this setup:
Modem -> router -> switch -> PC's.
The router will even have a few LAN ports you can attach PC's to.