Apple iTunes stores your music and other media files in the iTunes Media or iTunes Music folders. Unlike other music library applications, iTunes doesn't automatically add new music and other media files to your iTunes library when you place them in the iTunes Media or iTunes Music folder on your computer. You can add a folder to iTunes to force iTunes to scan the folder, importing any new media files from the folder into your iTunes library.
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Click the "File" menu in iTunes and select "Add Folder to Library."
Browse to the folder on your computer you want to add to the iTunes library. For example, force iTunes to scan your iTunes Media folder by browsing to the Library\Music\iTunes\iTunes Media folder on your computer.
Click the "Select Folder" button to start the scan. ITunes automatically scans the folder and adds any new media files to your iTunes library.