It depends on the subject you are shooting.
Aperature, in addition to controlling how much light enters the camera, is also your primary depth of field control. A small F stop has a wide aperature and lets in more light but it also has a shorter depth of field with a resulting shorter distance where things will be in focus.
This can be wonderful if you want a foreground subject in sharp focus against a softer background but is not what you want if you want a lot of things in the picture in focus. If you want as much as possble in focus, you need to use as large an F stop as the available light will alllow. A large F stop has a rmaller aperature and will let in less light requiring a longer exposure time to get a comparable exposure.
A larger F stops mean a slower shutter speed is needed to obtain the same exposure and this becomes the limiting factor. For fast moving subects with slow shutter speeds you have to track the subject so it has no relative motion in the frame but then the background will be blurred. Getting a fast moving subect against a sharp back ground means using a small F stop and short shutter speed but that will again limit the depth of field. There is always a tradeoff somewhere and understanding what does what and what it costs you will help you get the most of your camera and the avilable light.
Some cameras allow full control of both F stop and shutter speed either through a full manual mode or by allowing the user to intentionlly over or under expose by up to several f stops in either aperature or shutter mode.
But for the most part it is easier to switch between aperature and shutter priority modes and let the camera take care of the one that is not critical for the shot you are trying to get. You can then use the over/under exposure options to control for backlighting etc to get proper exposure on the subject.
Using natural light at depth you will find yourself forced toward slower shutter speeds and smaller F stops which will result in shorter depths of fields and less ability to "stop action" on moving targets. I'm not sure about your camera, but on my Oly I can change the ASA rating of the camera from 100, 200, 400 etc and just like with a film camera, I can get exposures in lower light but at some cost in image quality.
