Details about the STAR course, including how to enrol and who to contact, are available on the main University STAR section. The material covered in the STAR course is equivalent to COSC 131S1 and COSC 122S2, and uses the same assessment. Normally you should take the regular NCEA Programming and Computer Science standards through your school, even if you plan to take the STAR course.
The STAR course is intended for students who are doing well in NCEA (ideally in Programming and Computer Science standards if your school offers them) and wish to be stretched further.