I Know the feeling, have been digging around the net to get the answer as well.
In the end it turned out to be quit simple; but it’s hard to RTFM without the FM
In my setup I have all media stored on my NAS so XBMC will find the appropriate map and can browse through the files, my main folder is “Movies” and has some subfolders with TV shows and stuff for the kids in it.
Here’s the short how-to- select Video from the main menu, this will give you the folders on your device (either NAS or attached USB drive)
Highlight the folder , in my case “Movies” and press and hold the menu button on your remote, this will open a submenu
Select “set content” this will open a second menu where you can select the content movies/tv shows/music/none , scrapers and such.
Selct the appropriate scraper, run automated scan and hit “go”
Now it will start grabbing fan art and all other goodies.
I hve a few subfolder with TV shows, procedure is the same, do this in a seperate run , else all TV show subfolders will be tagged as movies