With Apple's iTunes program you can import songs into the iTunes music library to play in the program or transfer to a portable device, like an iPod. You can import songs from your CD collection or songs stored on your computer's hard drive. The hard drive you import songs from does not need to be an internal hard drive. You can also use an external drive.
Connect the external hard drive to your computer. If an autoplay menu pops-up, close it.
Open iTunes. Click the "File" menu and select "Add Folder to Library."
Navigate to the folder on the external drive that contains the songs. Highlight the folder, then click "Select Folder." iTunes will import any compatible files in the folder. You will have the option to add the songs to the "iTunes" folder on your computer. If you click "Yes," iTunes will copy the songs. If you click "No," iTunes will not copy the songs and you will need to have the external hard drive connected to your computer to play them or transfer them to a portable device.