Adding a Single ESXi Host to vCenter Server
You can use the vSphere Automation APIs to add a standalone host to a vCenter Server instance.
Add a single ESXi host to a vCenter Server instance by calling the create function and passing a com.vmware.vcenter.HostTypes.CreateSpec instance as parameter. When you create the host specification, make sure that you set the IP address or the DNS resolvable host name and the administrator credentials.