API credentials are necessary to access the Control Hub REST API. The credentials created will have the same access as the user who created the credentials. The credentials will consist of an ID and a token which must be used with every request to the REST API. These credentials are also necessary for use with Orchestration stages.

https://docs.streamsets.com/portal/platform-controlhub/controlhub/UserGuide/OrganizationSecurity/APICredentials_title.html

Users can find API calls via the UI -> Question mark icon (in the right upper corner) -> RESTful API.