It's very simple ..just turn your DHCP off in the ADSL router then the Internet Sharing connection will provide the IP address for you and enjoy your ADSL router as wi-fi device

It's very simple ..just disable your DHCP in the ADSL router and if u have shared your cable internet using Internet Sharing connection then the Internet Sharing connection will provide the IP address for you and enjoy your ADSL router as wi-fi device