To open the event, click on any one of the recurrences in the event series. Note that regardless of which recurrence you select, you will be taken to the original event date. This is because the recurrences are a mirror of the first date in the series and any changes made must be to the original booking.
Once you have the booking form open, you can amend the settings of the recurrence as you need.
You can also delete the recurrence at any time by selecting doesn't repeat from the dropdown menu on the event booking form.