Placing the clones
With your model brush active, press Space and click Insert Nanomesh. In the menu that appears below are the Target options. Leave this on the default setting to see how it works, by clicking and dragging on your base mesh. You should see a single cube appear, scaling and rotating as you move your cursor.
With the defaults you can see how a simple click and drag adds one mesh to another. The Model brush is actually more like a container for many different brushes. The Target Area enables you to define where your inserted meshes will go.