I am a just a car owner

If you do not have a switch to select "on" or "off" of a 4 wheel drive system, then it is a system that typically works on demand, to transfer power to wheels that do not slip in the rear of the vehicle when the going gets rough. No Hyundai I am aware of has a manual locking 4 wheel drive system to lock in engagement -- unless you see this button, it is not equipped that way.