If your music automatically transfered to your iTunes then it must have been Mac OSX right!? That's the only operating system this is possible where the music actually gets
copied to iTunes own library. Go to LW's Prefs>iTunes>Importing & tick enable to importing to iTunes & press the Apply button. Simple as that. Now you're set!
If you're talking about windows then you shouldn't need to do anything. Unless you enable daap. But that's intended for lan. See:
How to transfer music to my iPod (& iTunes)