The following is a step by step guide for adding a VMware ESXi 6.0 host to a VMware vCenter Server cluster as a scheduled task.

1. On the home screen of the VMware vSphere Web Client select Host and Clusters.
2. Select a cluster, then navigate to the Manage tab and select Scheduled Tasks.
3. Select Schedule a New Task and click Add Host….
4. On the Name and location portion of the Add Host (scheduled) dialog box enter the hostname or Internet Protocol (IP) address of the VMware ESXi 6.0 host then click Next.
5. On the Connection settings page enter the root authentication credentials and click Next.
6. On the Security Alert dialog box click Yes.
7. On the Host summary page review the configuration of the VMware ESXi 6.0 host and click Next.
8. On the Assign license page review the licensing information for the VMware ESXi 6.0 host and click Next.
9. On the Lockdown mode page accept the default settings and click Next.
10. On the Scheduling options page enter a Task name and Task description.
11. On the Scheduling options page click Change.
12. On the Configure Scheduler dialog box enter a time to add the VMware ESXi 6.0 host to the cluster then click OK.
13. On the Scheduling options page click Next.
14. On the Ready to complete page click Finish.
15. In the Recent Tasks pane verify a the Create scheduled task task completed successfully.