One end goes to the cigarette lighter socket, the other to a bulb. There are a couple of the assemblies on eBay but the pics aren't that great. Cant remember how exactly they attach, but on the cluster end, should be attached to a bulb socket.
Edit: coming back to me slowly lol. In the ashtray area there should be a small white plastic piece on top of I think it's the frame that holds the moving portion of the ashtray...it will have an angled hole in it that the other end of the fiber optic line fits into. I thought it was only a press fit but I can't say for certain there isn't supposed to be a bracket there.
I feel it has a brass colored metal end on it, opposite end of what is shown in the above pictures.