I cant get my pre-ordered song

Hello asho.smasho,

Thanks for the question. The following article outlines the procedure of pre-orders and redeeming the download:

Downloading a pre-ordered item

When a pre-order item becomes available, you will receive an email letting you know your pre-order is available for download.

If you've enabled iTunes to automatically download prepurchased content, then your pre-order content may already be downloaded to your library. If not, simply click the download link provided within your email notification, and your pre-order content will begin to download. Alternatively you can use the "Check for Available Downloads" feature in iTunes on your computer by choosing Store > Check for Available Downloads to begin downloading your pre-order.

iTunes Store: About Pre-orders

http://support.apple.com/kb/HT5714

Thanks,

Matt M.