Reference Article: https://docs.vmware.com/en/vCloud-Director/9.1/com.vmware.vcloud.spportal.doc/GUID-BEE4297F-8353-4DE3-8E86-DB2B511CAC77.html
Step 1:
Deploy vRealize Orchestrator, supported versions with vCD 9.1 are mentioned in below link:
https://partnerweb.vmware.com/comp_guide2/sim/interop_matrix.php#interop&224=2656&117=
Note: Orchestrator must be configured with vSphere authentication.
Step 2:
Make sure the vCD is registered to same vSphere (PSC) as vRO in the above step. Screenshot from lab:
Step 3:
Access URL: https://<VCD-IPorFQDN>/provider/libraries/service-admin/vro-registration
Click on “+” under registration
Step 4:
Fill in the below details:
Step 5:
Click on “Up arrow” icon in Trust Anchor and upload the vRO cert (Recommend is .pem format but .cer worked in my lab)
You will see vRO successfully registered: