You can only attach related diagrams to objects that have a Related Diagrams tab in their property sheet. 
        
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                Open the property sheet of the object and click the Related Diagrams tab.
            
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                Click the Add Objects tool to open a selection window.
            
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                	Select a model in the list, and then select the diagram to attach.
            
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                	Click OK to return to the object property sheet.
                 
                    The diagram is displayed in the list of related diagrams of the object.