If a shape feature you create is lacking a vertex, you may add one by using the Delete Vertex 
command. It may be helpful to select the features you wish to edit beforehand in order to display vertices.
1. To delete a vertex, click on the Delete Vertex command on the Feature Edit Tab. Clicking on the non-vertex part of a feature will select it.
2. To delete vertices, click on them or draw a selection polygon around them.