Unless you're talking about the light model itself, Blender isn't going to help much. What you need to do is to edit the model.cfg and add new lights under the "interiorlights" section. There are typically 5 types of lights: Fahrerlicht (driver's seat light), door_light, and lights_beleuchtung_[untenrechts/unterdeck/oberdeck] (lower deck front/lower deck rear/upper deck respectively). If you don't know what you're doing, just copy what you need and change the last three lines, which are the XYZ coordinates. You can get the coordinates in Blender.