How do you empty the oil on the Briggs and stratton 4.5 hp lawnmower to refill it?

How do you empty the oil on the Briggs and stratton 4.5 hp lawnmower to refill it?
there should be a drain plug under the mower where the blades are. to fill it is on the top where you check the oil.
there is a drain plug under the mower where the blade is. to fill it is where you chech your oil.

Many mowers do not have a drain plug, simply remove the dipstick and tip the mower on its side and dump it out the filler tube into a proper container.