As Jason replied there are no hydraulics tank for the HICAS on R33:s, so adding fluid to your HICAS system will be impossible..
On the other hand the HICAS on R32:s rely on the same system as the power-steering.. giving the result that Nissan Power Steering Fluid would be the one to use. (in R32:s)
The ATTESSA system (4WD-control) uses the same type of fluid.. So you would be correct filling either of the car models systems with the type mentioned above.
Your local Nissan dealer should be able to supply this, if corresponding fluids isn´t available at any petrol filling station or garage.
Its located under the steering colunm next to the bonnet catch lever (small pull out Compartment), and I seem to remember it been about the 5th fuse down from the left. Best to get it checked out, you don't want your rear wheels turning for no reason due to a malfunction at high speed!.