Here's how you do it. If the object is exportable, ie: Any imported mesh, native terrain or symetrical lattice. Click on the object to export, next click on the little "E" for Edit that is visible when the mesh is selected. This will open the Edit window displaying two spheres (one rough, one smooth). Now push (Command) D on a Mac and probably (Alt) D on a PC. This will open another window with export options. If you are exporting and imported mesh you can change the format if you like from DXF or 3DMF, to OBJ, 3DS, among others. Select the format you want and click save. If you are exporting a terrain there will be a different window with more options for exporting textures along with it. I hope that helps you, good luck.