To add an association class

[Nonchalant]

To add an association class - in the UML toolbox select Structure, find the Association Class icon and click once. Click on the source object in the diagram and hold the mouse down while you drag the line to the target element - release the mouse button. EA will draw the link and add the class. You will be prompted to add the class name - note that the name of the class and the link are the same.

But where is Structure, cannot find it in the UML toolbox?

[Nonchalant]

...i guess its just a normal class?

[AshK]

Association Class may be located in the Class toolbox.

Thank you for drawing our attention to this error in our help file.