DSR renders a game at a higher, more detailed resolution and shrinks the result back down to the resolution of your monitor - similar to the Down-sampling/Super Sampling used for high quality screenshots, but using a high-quality downsampling filter specifically designed for the task. To enable it, open the NVIDIA Control Panel, select 'Manage 3D settings', click the 'Global Settings' tab, find the 'DSR - Factors' field, tick all the boxes, click 'OK', and finally click 'Apply' on the bottom right of the window. In-game, you'll find seven new resolution options.