Maris, you can purchase the exam vouchers for SCEA exam (part 1, 2 and 3) at your local Sun center. Only part 1 (multiple choice exam) and part 3 (essay exam) are taken at your local Prometric center. For part 2 assignment, once you've made the payment at the local Sun center, you'll receive an instructions from Sun thru email of where/how to download the assignment's instructions in about 2 days.
HTH,
Joyce