The first thing I did, was create a polygon2D, create a circle with it. If you want to create the actual button, then I would go on paint, and I would use the circle tool to make a red, or whatever color you want it to be, and fill it in with that color. Next, you could select it, and copy it on to a piece of paper on word, and put that image into your godot folder. Now you can insert your red button into the polygon2D section, and wala, you got your self a noob way to make a button!