I had to do this also.  When you pay for the test, ADA verifies you're eligible (or not) to sit for the DAT.  They email you a letter stating you need special permission to take it more than 3 times.  What I did was email the person that sent the message, asking her what I needed to submit and if I could do so electronically.  She only replied the word 'yes'.  I emailed her my confirmation email from submission of my AADSAS app and in a day or two I received a new letter with the go ahead to schedule my exam (after 24 hours).  Hope this helps!!