Big rubber hose at the bottom of the radiator. Unclip that, and the coolant for the whole system will drain out. Quite a straightforward job. If you have the undertray still on your vehicle, you’ll have to take that off to get access. Again not a big job.
If you don’t know the history of the vehicle as far as servicing goes, you may as well change the oils on the rest of it while that engine tray is off. At least do the engine oil. Then I would be inclined to change the IRD oil, and transmission oil. Then you know you are all good with some nice clean stuff in the system. (There are many threads on here describing how it is done, and how you can tell how good a condition the transmission / IRD are in by looking at the state of the oil)
Back to the coolant question, when you refil, do it slowly so as to reduce the air in the system, and use the bleed screw on the rear of the engine bay. Keep any eye on levels for the first few trips in particular to see if any more air works itself out, and top up if necessary.
Jim