The process breaks down like this:
Start by identifying the major shapes in the image. There should be no more that 10 or 12.
Make a simple drawing that locates the shapes.
Paint in the first layer - the lights - of each shape, keeping the treatment as simple as possible (no texture or detail).
Now make two more first layer pages, so that you have 3 more or less identical sheets.
Put the second layer - middle value - on top of the first layer on two of your 3 sheets.
Finally, apply the 3rd layer - the darks - on top of one of the second layers.
In case you missed class, here are a couple of simple images that will resolve nicely into three layers. If you think there should be a fourth layer of super darks, put them on top of the three layer treatment.
Please read all that again. It's a little confusing, I'm afraid.