Helpinator’s Image Library allows you to add various shapes with text and arrows to your screenshots, making it easy to describe program UI. To enable it, first select image in the tree view, then select “Tools->Activate Shape Editor”. Then you should select style for the shapes, default is “Red and Yellow”, meaning red lines and arrows with yellow background. You can read more on how to create styles.
To add new shape:
1. Select it on the toolbar
2. Click anywhere on the image where you want to place it.