Explanation
1. Create Notifications Topic and Subscription
If a suitable Notifications topic doesn't already exist, then you must log in to the Console as a tenancy administrator and create it. Whether you use an existing topic or create a new one, add an email address as a subscription so that you can monitor that email account for notifications
2. Using the Console to Create a Rule
Use the Console to create a rule with a pattern that matches bucket creation events emitted by Object Storage. Specify the Notifications topic you created as an action to deliver matching events. To test your rule, create a bucket. Object Storage emits an event which triggers the action. Check the email specified in the subscription to receive your notification
https://docs.cloud.oracle.com/en-us/iaas/Content/Events/Concepts/eventsgetstarted.htm
https://docs.cloud.oracle.com/en-us/iaas/Content/Events/Concepts/filterevents.htm