Copying objects to the clipboard
When one or more objects are selected, you can copy those objects to the clipboard. To do that, press Ctrl+C, or choose the Copy item from the Edit menu. Alternatively, you can choose the Copy item from the right-click shortcut menu.
Pasting objects to the diagram
When you have copied the objects to the clipboard, you can paste them either into the current diagram or into another one.
To paste the objects from the clipboard into the diagram, press Ctrl-V or choose the Paste item from the Edit menu, you can also paste the objects by choosing the Paste item from the right-click shortcut menu.
Please note, that you can paste the objects not only into the current diagram, but into any other diagram. To do that, please, select the neccessary diagram from the list of the opened ones (this list can be found in the Windows menu), or open an existing diagram by selecting File | Open menu item. Certainly, you can also paste the objects into a new diagram.