In the WebUI, you go to Network->Routing->Destination. Then on that page, you click the new button in the upper-right hand part of the screen. Then you put 0.0.0.0 in the IP/ Address field, and 0.0.0.0 in the netmask field as well. Then you click on the gateway button, and put the 192.168.1.97 address in the Gateway IP address field. You also will want to select the external interface from the interface list. Then click on OK, and you should be up and going.
Ron