Re:What I want to know: Can I paint circles in it? (Score 1)

All I can tell you is: use the right tool! Gimp is not a vector-drawing tool, it's a raster image editing tool. If you want to draw circles and do other vector graphics stuff, use something like Inkscape. The export it to raster (or import the vector image from Gimp) to compose your drawing with the photos you were editing.