If you need to remove an event, you can do so by navigating to your dashboard and simply deactivating it.
If the distance of your event is changing, deactivate the current event that is being replaced, and then add a new distance by heading over to event setup, and then click “add another distance” in the menu.

To deactivate, click the edit link next to the distance…

Uncheck the box next to the distance…

Then click update.
