How do you create an Oracle black out please?

Summary:

Oracle Blackout

Content (please ensure you mask any confidential information):

We are trying to create a black out so that only four users can access Oracle for maintenance purposes on Purchase Orders.

Does any one have an idea how to do that?

Version (include the version you are using, if applicable):

Oracle Cloud

Code Snippet (add any code snippets that support your topic, if applicable):