Brush and pen tools will not work...

I have recently installed Painter 2015 and no matter how much I try, I simply cannot get my brush or pen tool to make any kind of mark when I move over to the white work area. The black pointer even disappears when I left click to try and paint. I'm sure that this must simply be a setting somewhere, somehow, but quite where or what that is, at the moment, is a complete mystery to me. If I can't get the tools to work, the program is useless to me. Any help would be most appreciated indeed.