International students must apply for a student visa to cover the period you intend to study in New Zealand. You must show evidence you have been accepted into a programme, paid your tuition fees and have sufficient funds to cover your living costs while in New Zealand. You must apply for your student visa before entering New Zealand.
Full details on the visa application are available through Immigration New Zealand www.immigration.govt.nz
You can locate the checklist for first time students here
You can locate the checklist for continuing students in New Zealand here