Hi there Poppee1,
You may want take a look at the article below for some more information on iTunes Pre-Orders.
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 Downloadsto begin downloading your pre-order.
Hope that helps,