This is your replacement stem. Note that the stem comes in two halves. The upper half will not need to be replaced.
First thing you will need to do is fold down your stem (refer to page 18 of your Owner's Manual).
Using the 6mm Allen wrench, loosen the stem binder bolt. Note: you will only need to loosen, not remove this bolt.
Taking the 8mm Allen wrench, remove the bolt and top cap. Note: Do not lift the bike once the top cap is removed. Doing so can cause the wheel and fork to separate from the bike frame.
With the stem binder bolt loosened and the top cap removed, you can remove the stem from the bike. Gently place the stem assembly next to the bike, being careful not to kink the cables.
Separate the upper and lower assembly of the stem by opening the quick release on the stem. Slide the two halves apart. Set aside the old lower assembly. Insert the upper assembly of the stem into the new lower assembly.
Reattach the reassembled stem onto the bike. Place the top cap back onto the stem. Replace bolt and tighten to just slight hand pressure.
Note: DO NOT OVER TIGHTEN.
With the top cap installed, raise, but do not lock the stem into the unfolded position. Check the alignment of the front wheel relative to the handlebar. Adjust accordingly.
With your alignment corrected, you can tighten the stem bolt to secure the stem onto the steerer tube.
NOTE: Make sure to thoroughly tighten the stem bolt.
Lower the stem and tighten the bolt of the top cap. This is to prevent the bolt from loosening over time.
Replacement is complete. Please ensure that all bolts are securely tighten. Test the tightness by straddling the wheel and gently trying to turn the handle bar. If the bar does not move independently of the wheel you are ok.