Go to Start--->Control Panel--->Network Connections
Once on that screen, you should see an icon titled "Wireless Network Connection".
If you do, make sure that it enabled. If not, use the Connection Wizard to create the new connection.
If none of that works, hit up the eMachines website, download and install any drivers that are related to wireless internet.
If none of that works, take the easy way out...Lug the thing to Best Buy, and let the Geek Squad set you up. If the computer has a wireless card, it shouldn't cost you more than 100 bucks to have them get you up and running....But still that is way way more expensive than it needs to be. Chances are, it's something fairly simple, and you'll feel dumb when you fork over the cash.