Welcome to the forum. Yes, you can use the node list to produce a world. In fact, I only use the main window. But it would be good to first study the opening scene if you're new to TG3. Open the fractal terrain shader and try changing some parameters (like displacement, seed...), and see the changes. Get to know how the principle works. The simple shape mask restricts the terrain, by the way. If you uncheck the mask, the terrain covers everything.
Add a lake, and see how that covers the world. You don't need to know specifics if it's just any terrain you want to create. If you want a specific terrain, with specific shapes, you could use the painted shader or paint a white on black (16 bit greyscale TIFF) mask in say Photoshop, and import that in an image map shader (set size, and displacement there).
And study some tutorials!!!