Cable modem --using ethernet/CAT5 cable-->
Wireless router --using airwaves-->
Most wireless routers have multiple ethernet ports. So, first connect your computer directly to the router, log in (manual should have default login/pass), set it up using same settings as you use on your computer (DHCP/Static, DNS Servers, ...). Also set up whether you want Encryption or not.
- disconnect cable between your computer & wireless router
- connect wireless router to cable modem
- plug wireless card into your computer
- connect your computer wirelessly to the wireless router
All the stuff I'm telling you should be in your wireless router's manual. Just post again if you have any more questions.