heyas; the easiest way, i think, to make the trail would be to go into the terrain editor and dig the trail in that. then, stick a plane or a cube (or cylinder... or another terrain, if you want) in the main terrain, with the material you want for the trail. it should poke out the trench you just made in your terrain and show up as the different material. as for the clouds... um... hmmm... well, as someone who can't ever seem to do anything with fuzzy and/or additive materials, i feel your pain. :) it says there should be a sample object called cloud? see if you can find the object or sample scene and check it out.