Check the Academy Admissions website, they will have information there. I believe that last year applications opened December 1st and closed sometime in January. I also think that they do require an ACT or SAT score. Good luck! It's an awesome experience!
They will accept the PSAT also. But its never to early to start taking the ACT and SAT tests. Check with your school for classes offered on how to take these tests there is a technique to it. It is common to plateau after three times.