I think, and I don't want to sound patronizing, that it's good to get to grips with the basics of TG before venturing into something as complex as a ringworld. If you open the plane, you'll see a default shader as it's surface shader. From there, you can point it to whichever node you want. The default is an internal node, but as soon as you point to a node outside an input will be there. Hope that gets you going.