buy wireless router...make sure it is 802.11b or 802.11g....i believe if you get the g, it is backwards compatible with the 802.11b so you will be fine.
FYI g is "better" than b
router will come with instructions but basically as matt said, plug modem into router....(will have to plug a computer into the router as well to set up security)....next, if you secure, will need to configure on your laptop wireless card (will detect and all you need to do is put in pword)