ok a couple of things: I have never used ENB before

so please forgive my stupidity.

Could someone explain what it is, how to use it and more importantly link to some places that give Skyrim dark nights and dungeons.

i have seen so many nice pictures that us ENB but I must admit I am a bit.....worried about using something I have no clue about.

please help.

Gopher has a video series that talks about ENB's and how to install them - https://www.youtube.com/watch?v=Mxl59pFXhTU&list=PLE7DlYarj-De1YrWupbcesibJIRZkMVB8

I recommend starting there.

Also keep in mind that the "darkness" you see does not effect stealth or NPC's stealth detection because they do not regester it. ENB effects are an overlay that do not effect the game engine. If you want that you'll have to get a mod that changed interior and exterior lighting like http://www.nexusmods.com/skyrim/mods/30450/? or http://www.nexusmods.com/skyrim/mods/30450/?. Both are compatible with ENB's but will changed how they were intended to look (usually not by much).