Navigate your web browser to sites that supply background music (see Resources). These sites allow users to purchase audio files as well as the rights to them (meaning you will not need to play royalties for using them in a publicly distributed video).
Search through the music databases and purchase the pieces that fit the mood you are trying to enhance with background music.
Start an email that will be sent to the intended recipient of the background music audio file. Click the "attach" button and browse for the music file you wish to attach (some email programs have only the image of a paperclip as the attachment button). Press "OK" to attach the music file to the email. Send the email.
Upload the music to an online file hosting website if you wish to send a very large file or multiple files. They are a better option for sending large information as they will not take up an email server space. Once the files are uploaded you will get a link that directs a user to a site to download the file. You can email this link to the recipient.