locking hubs have a nob in the center of the front tires of a 4wd vehicle. these "nobs" actually dissconnect the front tires or connect them to the front drivetrain. look in the center of your front rims and you will normally see indicators that say "lock" and "unlock" with arrows engraved in the plastic or metal of the nobs. If the vehicle is full time 4wd you shouldn't have these because it is designed to run all the time. Another possability is that many vehicles now have an A.D.D. (automatic dissconecting differential) system or something similar. To engauge the four wheel drive in these system generally involves just pulling a lever into 4wd or pushing a button because the 4wd is dissconnected in the front differential. Check your owners manual and you should find all the info you need. If you don't have one you may want to get one from your local dealer.
If you have any more questions I'm sure someone on here can help.
