If you have audio or video files on your computer, you can import them into iTunes so that they appear in your iTunes library.
Here are ways to add items from your computer to your iTunes library:
Drag a file or folder from the Finder to the iTunes window.
If you add a folder, all the files it contains are added to your library.
In iTunes, choose File > “Add to Library,” locate a file or folder, and then click Choose.
By default, iTunes places a copy of each audio file in the iTunes folder ([Home]/Music); the original file remains in the current location. For information about adding an alias to the file (instead of creating a copy), see Add items to your library without copying them to your iTunes folder.