Go to Smashits.com.
Click on a song title on the main page or enter a song, album title or artist into the search bar and click "Find."
Scroll down and click on one of the buttons located next to the song you want to download. The iTunes button will direct you to iTunes to download the song. The MP3 button will direct you to Amazon to download the song.
Download the necessary external music service application, either iTunes or Amazon's MP3 Downloader.
Register for an account at the music service. Submit your email address, credit card number and any other information the service requires of you to create a new account.
Log in to your account at the music service.
Click on the "Buy" button next to the song you want to download. Confirm your purchase by clicking on an "OK" button or entering your password, if prompted to.