You have to go to object maker, and type in what you want, then put .mesh behind it. For example, say you are wanting to put a waterfall in it. You would type in waterfall.mesh Save it in either Default, MyPlants, MyTrees, MyRocks, or Misc. and then go to your map. You should be able to place them in the map. When you export it, the meshes should show up in the map.