A great resource for understanding the type of lighting and sidelight sizes, is this :
http://www.titanicmodel.net/
Actually, it is a great site for understanding much about detailing Titanic.
I assume you may be new to working with small wiring and soldering, etc. When soldering it’s best to use lower heat on your solder iron as not to weaken the wires also, using electrical solder is Very important as well. A lot of people use fiber optics throughout to light portholes etc. On my Titanic, I used strips of LED to light the hull sidelights and general lighting of the windows . For Smaller lights, such as the deck lamps that I drilled out on the boat deck, running lights, mast light, and lights on the deck cargo cranes I used fiber optics. These were bundled together with shrink tubing attached to individual LED bulbs. To light the ceilings on B deck, I used pico lights, which are much smaller than a pin head. Very important that you use warm white bulbs for that yellowish glow as Titanic used Edison bulbs and had a very low light profile. Also, to bring a more balanced light throughout the windows of the ship I diffuse the light in the strip with a translucent film I obtained from a company called Stage Lighting. Again, the information source I gave you early in this post has great information for product sourcing as well, albeit they were acquired many years ago they are still good for the most part. A good source for lighting is Evans designs. They have great customer service department that will help you with any questions you have about their products and how to apply them. One more thing, plan ahead before you lay out your lighting and label your bundles for reference, as invariably a short will occur. I suggest you use a central “hub” to plug your bundles into before running them to the power source.
I hope I have answered your questions. If you need any more information I’ll be glad to help you Gary.
Happy modeling and Happy New Year!!!