Step 1: Go to computer store (CompUSA, BestBuy, Microcenter, etc) Step 2: purchase DSL/CableModem router for $20 (Seimens, Linksys, etc) or Step 2: purchase NetGear modem dial-up unit for about $60 or so. Step 3: take home. Unwrap. Plug into systems. Turn on. Enjoy. Note: if you're using a router that assigns DHCP, I can make a guess that this will do NAT gateway routing, too, so you PROBABLY already have what you need.
"I was in a computer game. Funny as hell, it was the most horrible thing I could think of."