There is a bracketing button on the front of the camera (just above the lens release button) - hold it down and use the rear wheel to select how many frames - eg 3, and front wheel to select the stops of exposure variation. So eg if you set it to 1.7 and then take the shots it will take 3 - one at the exposure you are using, one -1.7 and one +1.7.
Its best to put it on a tripod if you want to use the shots for HDR.