It is difficult to help you because your questions and answers are too brief and imprecise.
Please post the code you have tried. It is best to use a live example (e.g. Codepen, JSFiddle).
In these examples from the collection you can see how to access the vertices and change the shape.
CurvedArrowHelper
SineWaveGrooveRing
You can see the arrangement here: NumberingHelperExamples
In some places, vertices are in the same place!