You drain the oil from two places: 1) the bottom of the engine case, in the middle: there's a drain plug in the middle of a disc-like piece of steel and 2) the union that's in the middle of the oil line that goes from the oil tank to the oil cooler, it's just in front of the left rear wheel.
Most of the oil will be in the tank, and will drain from the oil line, but some of it will have flowed to the engine, hence the need to drain from the engine case.
Plus the oil filter, of course.
HTH.