Add Copy is located under My Calendar > Add Event > + Add Copy. In the following screenshot we can see the original event and two copies during the editing process.

When clicking Add Copy a new copy of the event will be added containing the same Start and End time as in the original event. You can then adjust the date and time of the copy as needed. Click the bottom Add Copy to add additional copies of the event.
Above we can see that I have added two copies using the same time but changing dates.
Clicking Cancel in an Event Copy will give the option to “Restore” (keeping the event copy) or “Remove” (deleting the copy). Restore really just means “Cancel the cancellation”, but using the same word was confusing…

This is a multi-day event.
Will show multiple events as one event on the front end. If used in relation with the Upcoming Events widget/shortcode or Today’s Events widget/shortcode.
When the rest of the event information has been filled out and you decide to Save Draft or Publish. Here is an example of saving the above original event and the additional two copies. A total of three events are now published. You can edit each event individually.

Here we can choose to View Event (front end) or Edit Event.
The following documentation shows an example with using + Add Copy and Repetition Pattern.