From Charting Shapes, drag a 1-D or 2-D word balloon, Horizontal callout, or Annotation shape onto the drawing page.
With the shape selected, type the text you want.
Drag the control handle or endpoint at the end of the pointer to change the pointer’s length or direction.
Tip: You can glue the endpoint of the annotation to a connection point on the chart or graph so that the annotation stays connected if you move the shape. To do this, select the entire shape — not a subshape — and then add a connection point. Drag the endpoint of your annotation shape to the connection point. If you resize the chart or graph, you may need to move the connection point. Click the Connection Point tool (on the arrow menu next to the Connector tool on the Standard toolbar), click the connection point, and then drag it to a new location.
Add annotations to graphs and charts in Visio