If you have a "lunchbox" locker (and Aussie is one) in the front axle, it engages automatically when you put the vehicle in 4wd and push the accelerator. I say that because it disengages when you let off the gas. It's automatic, unlike the Eaton or others where you have to flip a switch or pull a cable to engage. I hope this answered your question.
If you have one in the back, it engages in 2 or 4wd when you push the accellerator.