Once you have created a Rule, you can edit it, or delete it entirely. From the Rules page, look for the “Actions” column, on the right on the page. From there select either Edit (“pencil” icon), or Delete (“trash can” icon).
You can also re-order your Rules from the “Order” column of the Rules page. The rule order is descending, meaning that a rule at the top of the list will take priority over a rule below it.