Point your web browser to 192.168.0.1. I hope the admin password is included in the router documentation.
You should get the control panel for the D-Link 506L.
Indeed, 192.168.0.1 is the d-link control center as is dlinkrouter.local (no www). After going there, it was a matter of clicking Setup-->Internet-->Internet Connection Wizard. What I missed was that the D-Link wanted to be configured as a WiFi hotspot and not as a "DHCP Connection (Dynamic IP Address)." Otherwise, as a
The control panel does not need a password the first time but prompts you to set one while configuring the device.
That seemed to contradict everything I was expecting, because the TCP/IP Configurator in system setup seems to encourage the DHCP method. The connection and the 506L are now running quite well.
For what it's worth, the D-Link documentation states that there are two modes for the 506L: "Wireless Router Mode" (which I was using (with the ethernet cable)) and "Wi-Fi Hotspot Mode" (this what D-Link is calling them).
Thank you all so so much.