Access Point connect to Dlink Router sec

I support a office that uses both a wired lan and 802.11b. We have a D-Link DL-704 router that is connected to our DSL and we have a patch cable that goes from the access point to the router. Because the router is not the access point there is no were to setup additional security for the wireless connection. The routher assisgns the IP’s. The networking company that setup this configuration is no longer around. Is there anyway for me to access the access point to configure some security. The D-link router does not contain a client list so I have no idea what the IP address for the access point would be.

Any help would be great
Thanks