Fable's Star tool can be used to create stars, regular polygons, and complex shapes.
The Star tool can be accessed in the shapes submenu on the Toolbar.
To create a simple star:
Select the Star tool
Drag your cursor on the canvas to set the size of your star
Let go of your cursor to finish creating the star
If you'd like to keep a 1:1 aspect ratio, hold SHIFT while you drag.
Stars have the typical shape layer properties as well as a couple of custom controls. These can be found on the right side of the screen, in the shape layer's properties panel under Blend Mode and above Fill.
Width: Used to make the shape narrower or wider.
Height: Used to make the shape taller or shorter.
Point Count: Used to control the number of points on the star (minimum 3).
Ratio: Used to control the distance of the Star's inner points from the center. This is shown as a percentage of the Star's overall diameter.
Corner Radius: Used to round corners of a shape.