Welcome to the Community,
what you may need to do is:
- create a cluster and add the second host (the one with no powered on VMs)
- use the vSphere Client and connect directly to the host on which vCenter Server is running
- shut down vCenter Server and remove it from the host's inventory (don't remove from disk!)
- use the vSphere Client and connect directly to the second host
- add the vCenter Server VM to the inventory by right clicking its .vmx file in the datastore browser and power it on
- connect to the vCenter Server again and add the remaining host to the cluster
André