Hi,
Have you installed other components of vCenter server? Like the vCenter server, Inventory Service and SSO?
You cannot manage a standalone ESXi host using vSphere web client. To manage the host that you have just built you will have to use a c# client or what we call vSohere client. To download it you will have to point your browser to http://<esxi-ip> from a machine that can reach the ESXi and you will get an option to download the vSphere client.
If you have installed all the components of vcenter then login into Web client using administrator@vsphere.local and you will find the vcenter below hosts and clusters.