Ok, I have never used a Nikon, but I think I can figure it out by looking at a few pictures of the camera. First, you need to put it in a mode that allows you to adjust the shutter speed. Put the mode dial in "S" if you want to select just the shutter speed, and let the camera choose an appropriate aperture. To adjust the shutter speed, you will need to turn one of the two horizontal dials, that are under your thumb on the back of the camera, and below the shutter release on the front of the camera. But I don't know which one of these adjust the shutter speed, so you'll have to figure that out yourself.

Good luck with those motion blur shots!