Open your email account.
Click on the option to compose a new email.
Click on the option that allows you to attach a file/document.
Locate the MP3 file you want to send on your hard drive. Double-click on it or click on it and press the "Open" button. The MP3 file will upload to your email hosting service to be sent as an attachment.
Fill out the fields necessary to complete your message, such as the recipient's email address, subject and body, and click on the option to send your email.