Purchase a barcode from an independent retailer such as CDBaby. This is the easiest way to secure a barcode and these retailers will track the information from Soundscan for you.
Download the form located in the resources section to complete the information required to track your music recording. The form requires you to enter the song title, artist title, media type and UPC bar code.
Tracking sales requires a membership with Nielsen Soundscan. To sign up, visit their website and click the Contact Us link. They will create an account for you and inform you of any charges associated with your request.