The Insert Polygon tool (P) will add shapes too. But instead of having a predefined list of elements, you'll create your own thanks to some settings. Polygons can be defined when using the Polygon Properties. Click on the arrow to the right-hand side of the Insert Polygon tool icon and then choose Properties in the menu that appears.
Corners specifies how many sides you need. The default is 4 but can be increased to 999 (having so many sides is unnecessary for your polygon and will look like a circle at this point).
Rotation will turn your shape. It's the less important setting of this window because the rotation can be done afterwards, on the page, with the Rotation value in the PP or using the Rotate Item tool.
The Apply Factor checkbox just activates the last few options. It's interesting when you want to deactivate them all and come back to your regular polygon.
Factor will divide the sides in the middle and increase or decrease the radius at this point so that you can...