pass two exams(common and area tests). tests are held separately. Different track requires different area exams. I was applying for computational applied mathematics track. So, the area exam is based on numerical analysis skill and coding skill. next, I join one professor's research group and took a small project. when the project was finished, I was recruited. It's not hard if you prepare it. Also, at that time, they have extra funding and need student to contribute the coding skill to the open project.