Hello everyone, who ever is having the same problem please follow these steps:
1)Right click on desktop and choose "NVIDIA Control Settings"
2)Look at left panel,under
3D Settings --> Manage 3D settings
now you have 2 tabs GLOBAL SETTINGS and PROGRAM SETTINGS.
Under GLOBAL SETTINGS tab under "Preferred graphics processor" choose "High Performance NVIDIA processor". Don't change any other details on that tab.
Now,under PROGRAM SETTINGS tab
click the button ADD which will ask you to browse the program you want.Browse it to wherever your game is installed and find the ".exe" file.
choose the ".exe" file and click OK,the under "select the preferred graphics processor for this program" choose "High performance NVIDIA processor".
Click OK(if there is any) to save the changes and you're done.
Next time when you open your game it will run by NVIDIA card.