How do I use the fuse box?

Hello. I want to put a neon light under my dash and hooked up to my fuse box. I want to know how I can do that? The neon light I want has a cigarette adapter, which I have to cut. What do I do now after I cut the wire? I don't want to buy the neon light, then waste it buy cutting the wire and not know how to hook it up to the fuse. Thanks for any help.