Are you a student at NMIT? If so, you can park your car in the campus car parks. You'll need to ensure that you display a valid NMIT parking permit on your windscreen which gives you access between 8am and 5pm weekdays. This will be issued at the time of your enrolment.
If you are not a student, you will need to find alternative car parking. For a list of car parking sites in Nelson, visit Nelson City Council's car park page or check out the public transport options on the NBus page.