1) To Copy a performance, firstly you need to Edit the event. Go to the "Box-Office Page", and select the event of the performance you prefer to make a second copy. Click on "Edit" button to edit the event.
2) Now, in the 'Event Info' menu go to the "Performance" tab and select the check box placed next to the performance you wish to Copy. Now click on the Copy button above.
Note: The Start/End Date and the Start/End Time will be not be copied.