This is fairly easy to do. Go to Menu Aircraft, Edit Aircraft XXX, click Airframe, click Fuselage, click Engine. There you can edit the Smoke. If you wish to add smoke, right-cklick on Engine, choose Add Smoke Component. In the right window adjust Location in Parent (check the frame model for the exact location of the component), click Smoke Color - select/adjust Color by clickin onto the r-g-b- values. Then click onto Smoke Servo and select Smoke Servo. Adjust Smoke Size, Starting Size, Smoke Life etc. to your liking. You can add several smoke components this way. Make sure to activate them by selecting the Smoke Servo. You'll have to save the plane of course before exiting the editor. Hope this helps. Have Fun,
Daniel