"How Does My 4WD Work?" She AsksS

So my sister has had this car for about a year in a half, and we have snow in the forecast for tomorrow.
She calls me last night and asks, "How do I put my car in 4WD? Do I just press the button and go? What if there is 10 inches in the street? How do I use it?" It was a good question because I have no idea how any of these modern trucklett AWD systems work. Are they all the time? Are they push button? Do they require the vehicle to be in park, or can it be shifted on the fly? Who the hell knows?
Often pinged with simple little questions that are covered in the owners' manual, I have a copy downloaded on both my work and home machines so I can reference it - and I did.
I sent her this last night, and said, "Page 520 in your manual. Read this page."

She replied with, "Oh wow!!! Thank you. Um. Cliff Notes?"
I replied with, "That is the cliff notes. It's only one page."