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 destination element is highlighted.
An association link on the deployment diagram can be drawn between any two elements.
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 destination element is highlighted.
Related Topics:
Creating Links
Moving Links
Editing Links