This operation is quite straightforward:

1. Go to the Calendar page.
2. If you have access to more than one calendar, you will see a calendar dropdown near the top of the page.  Be sure to select the correct calendar.  Please note that if you are logged in as the Account Owner or an Administrator, you should select All Calendars from the dropdown on the left in order to see the Delete button.
3. In the Details section click Edit.
4. Click the Delete button and confirm the action.