2D Displace
I'd like to change the effect slightly. How do I get inside the node group to do this?
With the node selected in Blender, press the tab key. This will open up the node group for inspection and editing.
I load the file but I just get a cube or plane with no detail. What went wrong?
You will need to set the 3D viewport shading to Rendered mode to see the effect. You can do this by clicking the buttons in the top right of the viewport or, with the mouse in the viewport, press the Z key and select Rendered in the menu that appears..