You should visit the educational services office of the related faculty at the announced date and complete the online registration form. Then you will receive a temporary student card and follow the enrollment process by your student number.
Some useful information is available in the following files:
International Student Enrollment
Undergraduate Enrollment Steps
Undergraduate Enrollment (Required Documents)
MSc Enrollment Steps
MSc Enrollment (Required Documents)
Ph.D. Enrollment Steps
Ph.D. Enrollment (Required Documents)