I have the 1.25" version and it also came with the ND filter uninstalled. You need to unscrew the eyepiece holder and then the ND filter will screw into the bottom of it. You then reattach to the wedge.
Since the polarising filter is optional, this is screwed into whatever eyepiece you're using. I found this inconvenient so I bought a short extension tube from MyAstroShop:
http://myastroshop.com.au/products/d...sp?id=MAS-034A
The polariser stays on the bottom of the extension tube and then you can switch eyepieces as you like. Note that the MyAstroShop extension adds 26mm to the optical path and I can still reach focus. Bintel sells a similar one but it adds 35mm and I wouldn't be able to reach focus with it.
Hope this helps.
Morton