To enable select mode, click the  button on the Diagram pane tool bar.
 button on the Diagram pane tool bar. 
            
            
            
               
               - To select an object in a diagram, click it on the diagram canvas. Use Ctrl-click to select multiple objects, or click a blank
                  area of the canvas, then drag the mouse over multiple objects to “lasso” the objects. Selected objects are displayed with
                  handles that you can use to size the object.
               
- To select a relationship in a diagram, click it on the diagram canvas. The selected relationship is displayed in blue.