Turn the cam locks (in the spindle) CW to tighten.
Each cam should have a witness mark and each cam hole should have a set of three witness marks around the circumfrence. At 12o'clock is unlocked (load/unload), at around 4o'clock and 7o'clock are the tolerance marks for tightening the cams. The cam should turn past 4 but not past 7.
If it tightens before 4, take the chuck off and turn the stud out one turn. If it tightens after 7, take the chuck off and turn the stud in one turn.
If you need pics I can post them for you.
A Really good 3 jaw should give you .0005-.003" runout; a mid range chuck, .003-.01" and a REALLy poor one could be .02" or more.
Ignorance is curable through education.