You can deploy the vCenter Server Appliance only by using the Client Integration Plug-In, which is an HTML installer for Windows that you use to connect to the target server and deploy the vCenter Server Appliance on the server. You can connect directly to an ESXi 5.0.x, ESXi 5.1.x, ESXi 5.5.x, or ESXi 6.0.x host on which to deploy the appliance. You can also connect to a vCenter Server 5.0.x, vCenter Server 5.1.x, vCenter Server 5.5.x, or vCenter Server 6.0.x instance to deploy the appliance on an ESXi host or DRS cluster that resides in the vCenter Server inventory.
You cannot deploy the vCenter Server Appliance by using the vSphere Client or the vSphere Web Client. During the deployment of the vCenter Server Appliance you must provide various inputs, such as operating system and vCenter Single Sign-On passwords. If you try to deploy the appliance by using the vSphere Client or the vSphere Web Client, you are not prompted to provide such inputs and the deployment fails.