You can create an interaction reference from the Toolbox or Browser.
Use the Interaction Reference tool in the Toolbox. You can either click near the lifeline of an object to create an interaction reference attached to that lifeline, or click and hold while drawing a box that will overlap and attach to several lifelines.
The Select a sequence diagram dialog box opens to allow you to specify the sequence diagram to which the reference refers. Select an existing or new diagram and click OK.
Drag another sequence diagram from the browser and drop it into the present sequence diagram.
For general information about creating objects, see Core Features Guide > Modeling with PowerDesigner > Objects.