Create/Rotate/Move objects with Graphics and GDI+

Question

I'm working on a project wich kinda involves making some kind of improved "MsPaint" allowing the user to create a few types of figures, using GDI+ in C#. But since that kind of figures and the way to make them (drawLine, drawLines, drawRectangle) just make lines on a bitmap, I can't completely understand how to make a solid object from, for example, a triangle I made using 'drawlines' method.

For now I just simplified the sourcecode from an Addisson Wesley book "Addison Wesley - Graphics Programming With C Sharp And Gdi+" and I'm using it to learn the basics. Thing is, I'm not even sure if this starting point is the correct to ultimately make the program I wanna make, which as I said before, it should let the user to create "figures" or "objects from figures" and rotate, transform, move them around.

The source code is from this actual site:
http://www.c-sharpcorner.com/Store/Books/0-321-16077-0.asp
I only used Chapter 03 "GDI+ Painter" as I think it could help.

Thank you very much in advanced. I attached the simplified version wich only allows to draw simple lines ellipses and rectangles based on the mentioned GDI+ Painter.