You may not want to set it up manually. If you're ever asked to bypass your WAP (such as by Earthlink - they're like most ISPs when they say that they can't support home networking), they probably want your computer to get information via DHCP (automatically).

Have you tried power-cycling (unplugging the power for about 30-60 seconds) the router/WAP as well as the cable modem? Sometimes they need to be refreshed to update the network status. If you do those, you may need to restart your computers to renew their IP addresses.