Loosen "the 2 on the side", then tighten the one on top. This will load the headset, and reduce play. Don't over-tighten, or you'll make the steering stiff/difficult. After you have that done, make sure the bars are straight, then tighten those side bolts. They should be pretty snug, cuz you don't want your stem to flop around, or come off, while riding. The Parktool website can help you, if you still have trouble. Good luck.