For NVIDIA Graphics Cards
- Open the Nvidia Control Panel. You can do this by right-clicking on the desktop
- Select Manage 3D Settings under 3D Settings
- Click on the "Program Settings" tab and select Generation Zero (or add its directory)
- From the second option "Select the preferred graphics processor for this program", select High-performance Nvidia processor from the drop down list (you can see what the automatic option is listed as global setting).
If you do not see the second option, it means you only have one GPU and you should not be concerned about the game running on it.
For ATI/AMD graphics cards
Open the control center in the same way as above. You may need to open graphics then PowerPlay and set plugged in and/or battery to maximise performance. You can also try going to graphics then 3D and move the slider to performance. Your computer may also have a switchable graphics tab where you can change the settings for individual programs.