Partners of New Zealand citizens, residence visa holders, and work visa holders are usually able to apply for a work visa on the basis of the relationship. If the application is successful then you will be granted a partnership work visa which will have the same expiry date as your sponsoring partner, and it will be an open work visa allowing you to work for any employers in New Zealand.
You will need to satisfy each of the following requirements:
Let's take a look at each of them in turn.
General requirements include paying correct application fee, using prescribed Immigration New Zealand form, meeting health/character requirements, and being a 'bona fide' (genuine) applicant.
While there is no requirement as to how long you must have been together with your partner, the relevant Immigration instructions requires that you must be living together with your partner in a "genuine and stable" relationship. It is therefore a two-part test where you have to show that you are living together physically, and that your relationship is genuine and stable.
Your sponsoring partner must not have character issues, such as having been convicted for any offences involving domestic violence or of a sexual nature, having been fraudulent with Immigration New Zealand previously, etc.
Many issues that you were not aware of could surface when you lodge an Partnership work visa application, so it will be worth getting proper advice and guidance from the beginning.