They are not adjustable, they have hydrolic lifters, if yours are noisey then I suggest you get down to your local dealer to do them for you under warranty.
They are not very easy to change, fairly involved jod, cambelt has to be removed, the rocker box also holds the cams in place etc etc.
Dealer only mate, I would not suggest stripping it down or anything yourself as special locking tools are required.
Seems strange that yours is noisey