How to set a default graphics card

For NVIDIA Graphics Cards

1. Open the Nvidia Control Panel. You can do this by right-clicking on the desktop.

2. Select Manage 3D Settings under 3D Settings.

3. Click on the "Program Settings" tab and select the theHunter game.

4. 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).

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 maximize 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.

For Windows 10 users

Please refer to below page: 

How to Choose Which GPU a Game Uses on Windows 10