Click on the event's Show Details. Click on the Change Status button. It is listed under Performances on the Show Details page.

Once you click on the Change Status button, the following options will appear. Select Resume or Reschedule.

Select Resume if you are still hosting the previously HELD event at the same time.

Click the Reschedule to change the date and time of your previously HELD event.

You will be promoted to input the desired reschedule dates as shown below. Make sure to click "Save" before moving to the next step.