I don't have Geforce Experience installed, so I can't really comment on that. I have read that it will apply automatically for the game where GFE supports it.
In the Nvidia Control Panel, the only place you will see it is under Global Settings, right under the setting for "CUDA-GPUs". In there, you can check off all the boxes if you want. Then when you go to your actual game, you will then have resolutions above your native display available, depending on what your game supports. Whatever you checked in the Nv Control Panel will determine what will be available in-game, so I check off all of them.