Press down again and now move the mouse. You can draw several different standard shapes. To do this Click on the shape icon. This is a rectangle with solid lines, not dashes, for an outline and it is called Shapes. A set of options will appear.
Line indicates the size of the outlining line.
The values 3-8 are generally okay. Style gives you the choice of outline or filled. You now move the cursor to the image. It will change to a cross hair next to a rectangle. It is a rectangle even if you made another choice of shape.