Import media from a computer to iTunes on Mac
In the iTunes app on your Mac, choose File > Add to Library.
Locate a file or folder, then click Open.
If you add a folder, all the files it contains are added to your library.
Tip: You can also drag a file or folder from the Finder to the iTunes window to import it.
By default, iTunes places a copy of each audio file in the iTunes folder (Home/Music/iTunes/iTunes Media) and leaves the original file in the current location. For information about adding an alias to the file (instead of creating a copy), see Change where your files are stored.
To learn how to add other content to iTunes, see How to add items.