@Stephen Keating Thank you for reaching out to us, As I understand you are looking for documentation to setup OCI (Oracle Cloud Infrastructure) with Microsoft Sentinel.
You can refer to these links, detailed steps have been provided here -
https://docs.oracle.com/en/learn/oci-logs-ms-azure-sentinel/index.html#introduction
Not sure why you are not able to see OCI under Content hub, just like below, Billing is based on the volume of data analyzed in Microsoft Sentinel and stored in the Log Analytics workspace.
Let me know if the above links help you in configuring the OCI with Sentinel, if not we can connect offline to discuss further on the same.