Tutorial
Polygons in Sketchup
What is it?
Polygons are flat shapes consisting of straight lines that are joined to form a closed chain or circuit. They are planes that are bounded by closed paths, composed of finite sequences of straight line segments. The lines of the polygons are called edges or sides, and the points where two edges meet are the polygon's vertices (singular: vertex) or corners. An ngon is a polygon with n sides. The interior of the polygon is sometimes called its body.What's the tutorial?
Drawing Polygons
 Select the Polygon tool

Click the ground plane (the ground plane is created by the red and green axes.) and type the number of sides you want, followed by an s. To create a pentagon, type 5s and press Enter.

To finish drawing the polygon, pull out to the size you want, and then click to set the edges.
 If you want to create a polygon aligned to a different plane:

Select the Polygon tool.

Move out to the top edges of the drawing until the cursor changes to a red or green polygon.

Press and hold the Shift key to lock that inference direction.

Move to the point where you want to draw the polygon, and then click to set the centerpoint. Set the sides by typing a number followed by s in the Measurement toolbar:

Finish drawing the polygon.

Select the Polygon tool.
Circles and Polygons
Circles and polygons have the same adjustments. You can change both the radius and the number of segments. The difference between them is that they extrude differently with the Push/Pull tool (P).You can convert your circles to polygons with the Convert to Polygon tool in the CTRL+click Context menu. If you start modeling with circles, but later need visible edges, use Convert to Polygon to change the edge smoothness property of the circles without exploding the circles into individual segments.
When you use the Push/Pull tool (P) with the converted circle hold CTRL on Windows and SHIFT+OPTION on Mac OS:
Now what?
 Create a model with polygons.