These are easy to insert - just drill a 1/8” diameter hole in the layout and insert the fiber through the hole and then the base of the lamp, which will be a snug fit into the 1/8” diameter hole. Then insert the fiber beneath the layout into the Lamplighter box.  Each lamp comes with 4’ (~1.3m) of 1mm fiber optic already attached to allow easy placement in proximity to the Lamplighter box. If the height of the lamp needs to be decreased, just insert it further into the hole in the layout.

The Dwarvin Street Lamps add interest to the layout without being obtrusive.  They provide directional lighting, which is what would be seen in streets prior to the advent of the mercury vapor lights that become widespread in the 1970's.  The article on Directional Lighting provides a bit more background on this subject. 

To change the ambiance / color, add a drop of translucent paint to either end of the fiber.  If you add it to the end of the fiber that is inserted into the Lamplighter, then make sure the paint is dry prior to inserting the fiber into the Lamplighter box.  See the video on how to do this.  To create an old world look, I use the Tamiya X-26 Orange Translucent paint, however, you may use whatever paint you like or even a colored marker.