You must give access to a source of VM templates, so that the DevOps engineers can use them to provision VMs in a self-service manner. To give access, you associate a content library with VM templates to the namespace used by the DevOps engineers.
You can add multiple content libraries to a namespace that has the VM Service enabled or the same content library to several namespaces. You associate a content library to a namespace when you create a new namespace, update or reconfigure an existing one.
To make the VM Service aware of the content libraries in your environment that the DevOps engineers can use to self-service VMs, you must use the NamespacesInstancesVMServiceSpec data structure which is part of the namespace create specification. The instance contains a list of content libraries that will be used by the VM Service. You can specify this list with the content_libraries property.
You can also associate one or more VM classes with the namespace. See Associating a VM Class with a vSphere Namespace.