Sorry.. I wasn't clear.. I continued onto the "Land Clip" step to get the colour levels, but didn't get the effect I wanted, so I kept moving back and forth between the two steps to see where I went wrong. I managed to get the Land Noise (Filter/Render/Clouds/Solid Noise) done right, with "Layers:Overlay" from the Layers Dock, and then created a New Layer (Land Clip), fill type:White; Lighten Only. Then I adjusted the Colour Levels to Output(71) (as in tutorial.. I know the actual number can be different). What I get is white "land" and gray "sea", with no cloud-like "landmass".
here is what I've been able to do so far: