The maintenance manual has specific instruction on how to add the NAS modules. Also, there is a procedure on TISC,MK-92HNAS075-02, that contains the bulk of the instructions (plus some extra info for a separate process).
One of the main things is that you must be using the MPC software (not the SVP image) whilst on the maintenance network.
You would be well served to contact the local Hitachi Vantara contacts for more detailed assistance.