Got ya...
First, click on the home tab. Over to the right, you should see something akin to "Welcome, (your name)..." You should see something that says "Quick Links," and under that, stuff like "Redeem," "Buy iTunes Gifts," etc. Click the one that says "Account." It's like the fifth one down on mine. You'll be prompted to login with your password.
You should now see a screen that says, "Apple Account Information." The first bit is your information, email address, etc. About the middle of the screen, you should see something that says, "Most Recent Purchase," with a "Purchase History" button to the right of it. Beneath that button, you should see a button that says "Manage Preorders." Click on that.
You should see a listing for ATS on the "Manage Preorders" page.