the 'Limewire Tunes' is just a playlist & those files aren't actually in the iTunes library, so you won't be able to move or edit files within that playlist.
Instead, you need to find LW's saved folder. Within LW tools > options > saving will show you the location. If you go to LW's library, hughlight a file & click Explore...your saved folder will open. You need to add files from this saved folder to the iTunes library

There's heaps of info here.
Transferring music to iPod & iTunes