Not a stupid question! To change the default render settings for Bryce, click the arrow next to the render button (see image). Choose your Quality Mode, then your Rays Per Pixel. The best way to see results, in my opinion, is to render your image in default, change your settings, then use the plop render to re-render certain areas. When I started playing with settings I would, for example, split a face in half so I could compare results. Of course, the more rays per pixel you use the longer it will take your image to render.