UV Mapper is fairly easy to use. Just takes knowledge of your model and how it should look when laid out flat (otherwise if UV Mapper does something strange, you'll be lost). You import an obj object into UV Mapper and if your model came from RDS, it probably looks like gibberish. To clean it up, select "New UV Map" from the "Edit" menu. The default selections are usually fine. You should have a better map now. You can move around polygons if they are overlapping, or move just vertices ("Select By" menu item). Move polys/vertices around until no polygons or lines overlap. Save the model to save your new map. To actually make a texture map, you can also select "Save Texture Map" from the "File" menu. It saves an 8-bit BMP file.