Hi. The registration process for New Zealand does seem to be complex at first but it's really not. It's just very subjective and you have to provide detailed information, which can make it look daunting.
I'll try to break it down for you:
First, you need to look at the forms given for overseas applicants on the New Zealand Physiotherapy Board's website. There's an application pack of about 9 documents, which also contains guiding documents to tell you how to fill the forms.
Read those forms and guidance notes and ensure that you have the required IELTS/OET score as well as the necessary documents at hand, e.g. your passport, physiotherapy degree, transcript, curriculum, etc.
Once you are certain that you have the necessary documents and fulfill the requirements, you can start filling out the forms using the guidance notes for help.
If you can be a bit more specific about the particular thing you're having difficulty with, I might be able to provide more help.