If I remember correctly, first you have to go to the
ADA page and register for a DENTPIN. Then, you have to apply to take the DAT & pay the testing fee of $445 (may have increased)
here. Afterwards, the ADA will determine if you are eligible to take the DAT, and if so, you will receive an email with an ID and instructions on how to register for a test date on the Prometric website. You can only see the dates when you have your Eligibility ID. Hope this helps.