How do you change oil in model no 917376741 craftsman walk behind mower?

On my Craftsman Lawn Mower, I have to raise the lawn mower or tilt it on it's side, and underneath where the blade is, there is a large drain plug. Take it off and catch the oil. This is a great time to clean the underside of your lawn mower and either sharpen or replace your blade.....Nothing cuts better than a sharp blade!