how do I assign a texture to a model ? I know about mts files . but I can't get it to work ...... sorry if this seems dumb :-(

We support UV-mapping of textures, so you just create UV mapping in your authoring application. If you have an ASE file for example with already established UV mapping but no image then you can load that image (i.e. JPEG) in either Scene Builder of Stream Tuning Studio.