Create some spheres (or you can use rocks for rougher cloud surfaces or a terrain if the clouds completely shroud an area of ground) and size and position them to get the general shape of your clouds. Apply one of the cloud materials from the "volumetrics" tab (I think, don't have Vue on my machine here at work) of the material library to each sphere (or other object). Then fiddle about with size, position, shape and material settings until you get the exact look you're aiming for. -- Mark

Mark