It's not that simple. In order to sit the written (there's only one) you have to complete an ATP Certificate Training Program. As of now there are only a handful of approved programs. And you can't just jump in a sim and take a checkride for a type rating. There must be a record of ground and flight training given by a FAA Instructor who signs you off for the checkride. There are only 2 active EMB-120 and 2 active SA-227 sims in the country, all run by Flight Safety. Flight Safety is also one of the ATP CTP providers and they do the course in Atlanta where one of the EMB-120 sims is located. I'd start there.