[Ronn_Bman]

The hak filename should be something like XXXXXXXXX.hak, so just copy/move that downloaded file into your "C:\Neverwinter Nights\NWN\haks" folder. It has to be have a hak file extension, so if you haven't unzipped it etc., do that first.

That's assuming you installed it to the default location. If you didn't, figure out where you did install it and copy/move your hak file into the hak folder as above.