Probably the easiest way to do it is to get a netgear adsl wireless router. That way, your phone line plug's into it. Then you can either run a rj45 (network) cable from the router to the pc (reccommended) or, get a wileless usb adapter, or a pci wireless adaptor that will do inside your computer and job's done.

The network cable route will give you faster transfer rates

This is my router that sit's on my desk, although I have Telewest Broadband and it's a cable modem, the principle is the same.