This tutorial covers adding XY data to ArcGIS, so that you can view and work with the data in ArcGIS. By XY data I mean point data such as foliation that has a spatial (XY) component associated with it.
This page explains grid reference systems, with specific emphasis on New Zealand. If you are interested in making a grid reference system for your map read this page and then see:
What is a grid reference system?
A grid reference system is a simplified grid used for a map area to make reporting and looking up coordinates easier.