There should be a wireless network icon near the system clock in Windows. Clicking on that will usually scan for available wireless networks in the area. Then it's just a matter of selecting on and supplying a password if needed.

 

You need a wireless card and a wireless router, as obvious as that might sound.

Wireless only has a range of 50-100 ft inside a house, so you won't be able to go too far.... If you're thinking of using wireless Internet miles away, you may want to invest in wireless Internet via your cell phone provider. It's pricey and requires an additional PCMCIA card, but it lets you get high speed almost anywhere.