Hi Qiang
I´m having the same issue and even though after a while something can be found from help.sap.com, it does not work quite like it used to work in ES Workplace. Maybe it´s just me, but information is harder to come by and certain information is missing.
Please check for example the following links to find similar information on ES´s from help.sap.com:
Enterprise Services in SAP ERP
Enterprise Services in SAP for Retail
One can also still access the ES Workplace from the 'Access Now' option shown in your screen shot, but who knows for how long. (Seriously, does anyone know? I´d definitely like to 
)
BR
Antti