[Correct location for map (.dds) file?]

Tried this on two subreddits to no avail.

 

How can I get a custom map into a custom world space? Whenever I try, I get an invalid directory error.

Please help

[I have an idea, and I am in need of some serious assistance]

I have had an idea for a new New Lands mod for Fallout 4. Problem is, I have no damn clue how to get any kind of mod creating software to function properly. I am in no way a programmer or modder. A section of Long Island, NY, to be added as a "community DLC" for FO4. New factions, weapons, clothing, and worldspace, all with custom meshes and textures. I know this probably won't get noticed, but if it does, I have an offer; I have a storyline in mind, I have concept art, and I have characters. I understand that these kinds of mods take an exceptionally long amount of time, and I will be sympathetic if this idea is too difficult of a project. I have an idea, and I really want to make it happen.