In order to use the vSphere web client to manage the vCenter Server, I have to register the server first.
1) https://localhost:9443/admin-app
2) Click Register vCenter Server URL
3) Enter the vCenter Server IP, username, password information, and vSphere Web Client server name or IP
The error message displayed:
VMware ESX and VMware ESXi servers are not supported with vSphere Web Client 5.0.0.