Start with the basics.. You know the larger the F number the smaller the aperture correct.? In other words F/2.7 is wide open, F/22 is as small as most standard lenses go. You're going to have a hard time doing this because this camera is not designed with any manual mode. The lens will close to a minimum aperture of F/8. Figure out how to make that possible and that is the best you are going to achieve. Point and Shoots are designed for just that, make a simple operation of taking a picture. They are limited when asked to do what you intend to do. There is a way, as described in my first post, but there is no straight forward way to set the camera specifically to do what you want.
Again, low ISO, with slow shutter speed will force the camera to use a small aperture. It helps once you understand the basic trade offs between ISO, shutter speed, aperture and available light. I suspect that this is another goal on this assignment.