PC with 2 graphic cards problem

[Heaven Fall]

Hy
I have a PC with 2 graphic cards
The first intel 4600 and second gt840M

The game detect only the Intel cards and take the low parameter or I think with my Nvidia i can have medium or also high ( maybe ^^ )
But in the graphic option menu at the start he show me only my fu**ing intel card.
How to change it?

Thanks for your help :)

[Madness]

https://www.youtube.com/watch?v=mutQBjfs0P0

[Heaven Fall]

Thanks ^^