Those cranks look used, are the flats on the square-taper clean and pristine?
Be sure to get a torque-wrench and tighten the crankarm bolts to 30-35 lb*ft. You have pretty much just one chance to install them correctly. If the bolts aren't tight enough, the cranks will wobble loose and the bottom-bracket spindle will gouge out the square-taper. The cranks will never ever fit correctly again after that and will come lose no matter how tight you crank down on the crankarm bolts.