Just tip it spark plug uppermost, and drain the oil from the dipstick/filler tube.
Probably best to run the fuel level right down first, as the tanks on these are prone to splitting along the seam.
There is a square or hex drive socket head drain plug underneath, but using it is a complete PITA, as the blade disc has to be removed. And you need a mower workstand, with some way of holding a catch container in the right place.
