You can add notes to a diagram for clarification or any other purpose.
Notes appear only on the diagram; they are not stored in the model or
in generated code.
Create a diagram or edit an existing one.
In the Other drawer of the Component Designer palette,
click Diagram Note.
Click on the canvas where you want to place the note.
Click once in the note rectangle to make the text editable, and enter the text
of the note. You can resize the rectangle by dragging its borders.
Optionally, you can add a link to associate the note visually with a component
in the diagram. Click Note Link in the
Relationships drawer of the Component
Designer palette. Click the note first, and then click the
component that you want to link the note to. A broken line connects the two
entities.