R6020 as second router

I purchased the router thinking I would be able to establish a wireless intranet within an existing wired net. The reason is, I want to support a portable environment for teaching robotics, and the robots are wireless. I started to install the router, as a second router, using instructions at http://www.wikihow.com/Connect-One-Router-to-Another-to-Expand-a-Network

When it came time to access the Netgear AC750, I tried the genie app, which complained about not being able to reach my ISP (which makes sense, because in the wikihow instructions, the ISP is not available.) and then I tried reading the manual at http://www.downloads.netgear.com/files/GDC/R6020/R6020_UM_EN.pdf, and it appears to me that the AC750 R6020 will not permit configuration unless an ISP is available. I hope I am mistaken. Please tell me whether I can access the router without having the ISP on hand, and if so, how.