Click the Generalization/Implementation Link button 
on the diagram toolbar.
Click the source element.
Drag the link to the destination element.
Drop when the second element is highlighted.
A generalization/implementation relationship link can be drawn between two elements of the same type, for example, between two classes or between two interfaces. This relationships link may also be drawn between a class and an interface where the class is the client and the interface is the supplier.
To create a generalization/implementation link:
Click the Generalization/Implementation Link button
on the diagram toolbar.
Click the source element.
Drag the link to the destination element.
Drop when the second element is highlighted.
Tip: Double click the link on the diagram to display the source code in the Editor.
Related Topics:
Creating Links
Moving Links
Editing Links