The MAPS.NZ2 will have information about the ID values. It contains Island, Region and IdName which have values that look like city or district names. Being a yank I have no idea what a domicile code or DHB might be.
Most of the map data sets provided by SAS include political areas.
The Lat and Long, as do the X and Y variables, are points on the area boundary.
To map with the MAPS.NZ or MAPSGSF.NZ or other data sets in those libraries you would need to use another data source to provide lat/long values for your domicile code and project them to the map data set.
If your domicile code is similar to the US Zipcode, which represents a postal delivery area that may be a few city blocks or several hundred square miles an example of plotting points on a large area map is at : https://support.sas.com/kb/42/426.html SAS provides a data set that allows a look up of Zip code to geographic center of the area in lat/long terms. You likely need a similar data set.