Click the Associates Link button 
on the diagram toolbar.
On the Diagram, click the source element.
Drag the link to the destination element.
Drop when the second element is highlighted.
An association link on a collaboration diagram can be drawn between any element.
To create an association link:
Click the Associates Link button
on the diagram toolbar.
On the Diagram, click the source element.
Drag the link to the destination element.
Drop when the second element is highlighted.
Related Topics:
Creating Links
Moving Links
Editing Links