You need to take the upper triple clamp off of the bike to give you access to the nut. It requires a spanner wrench to adjust properly (not in the tool kit). You can also use a punch and hammer to adjust it :badteeth:, but this won't give you fine control over the tightness. Once you get access to it, you need to make sure the front end is off of the ground and able to be turned freely by hand. Then you slowly tighten the nut to the point that you can feel the front end starting to bind. The nut will be at the proper tightness just before that point. The front must be not have any resistance to turning freely.
I doubt it's loose though. Just tighten the top nut to the torque setting swjohney gave you and you should be all set. Now, if you do get some knocking under braking or over bumpy pavement or some front end vibration under braking, then you need to turn your attention to the head bearings.