In order to have your music sold on Myspace, you'll need to have your content delivered to Myspace from one of the digital distributors we partner with such as CD Baby or Tunecore. You'll want to contact your rep and work with them to have your content delivered and targeted to your artist profile. Just make sure they're delivering the same UPC and ISRC info to Amazon/iTunes and Myspace Music.
Once the distributor targets your content to your artist profile, your profile will have the official logo when searched under Music, albums will show up under the Music tab on your profile, and the content within that album will have enabled buy links. This won't populate buy links on the profile player level, only on the albums under the Music tab.