To do that you need to logon the WebUI using APP userid.
Once you are connected to the VantageDB (so in offline mode), you can then add HOST definition.
You need to enter for each HOST the ip address to connect to it as the port number matching the one the Ca Vantage host STC uses.
Once done save the HOST definition into the WebUI and Logoff from APP.
You should then be able to list the HOST defined and logon to them.