FPS = frame per second. It is a measurement of how fast your machine can draw, not a setting you can make.
The way most OpenGL based graphics programs work, is that they draw farmes as fast as they possibly can. The more things that they have to draw, the longer it takes to draw a frame. So Frames-Per-Second is a handy way to measure what sort of performance you are getting from your system.
As a point of reference, the human eye sees about 24 frame per second. If your system is displaying faster than that, it will look \"smooth\" to your eye. If it is displaying shorter than that, it will look \"jerky\".
So what you want to do is tweak the settings you can tweak until the FPS is more than 24.