Aha! Whiteboards | Annotation shapes
Use the annotation shape to add context to any object or area of your whiteboard — so you can highlight key concepts that you want to point out or discuss further with your collaborators.
Access your Shapes toolbar and select the annotation shape.
Drag the end of the shape's connector to the object or area of your whiteboard that you need to comment on.
Double-click the annotation shape to add text.
Right-click to format its color, border, and text.