Probably not the answers you want to hear, but:

With existing light (no flash, your "outside light"), the aperture setting depends on shutter speed and film ISO rating (speed).

With flash, the aperture depends on the "guide number" of the flash (a rating of the output power) and the film ISO rating. The shutter speed is set to the "sync speed" or slower (usually 1/60 or 1/125 depending on the camera).

They're simple questions but they have complicated answers. A basic photography book will help a lot, some of these concepts are easier to explain with drawings and images.