Creating a use case diagram
1. Locate the item that is to own the Use Case Diagram, that is, a Class, Data Type, Interface, Package, Signal or the Model.
2. Right-click the owning item:
◦ Point to New and then click Use Case Diagram.
or
◦ Point to New, point to UML, point to Behavior, and then click Use Case Diagram.
3. Type the name of the Use Case Diagram and then press the Enter key.