It is pretty easy to accidentally tighten the stem clamp bolts before tightening down the headcap, so it's a good idea to make sure this is installed correctly. This is important because the top cap bolt pulls the whole assembly tight. Then when you tighten the stem clamp bolts, it locks it in place. Having a loose headcap can cause a creaking noise.
There is a test on the back of the instructions to ensure proper installation. (see below)