When you insert a CD into a computer with iTunes, a prompt appears asking whether you want to view it on the desktop, play it or import it. However, when an MP3 file is on the computer but not in iTunes, you must import it into your library to play it in iTunes.
Go to the “File” menu and select “Add to Library.”
Navigate to the location of the file in the “Add to Library” window. Click on the file to select it and press the “Choose” button. Alternatively, drag the file into the library and drop it. The MP3 file will be imported into the iTunes library.