I've bought two bikes that came with a "manual." For all the adjustments @
BirdsBikeBinocsmention, they say, roughly, "Take it to your bike shop for adjustment." I suspect that's for two reasons. First, as noted, the OEM manuals have all the details on how to adjust the parts. Second, it's a legal defense mechanism; if you mis-adjust something and get hurt as a result, well, you were told to have it professionally adjusted.
If you want to know how to fix your own bike, either buy a good book or look at the Park Tools website.