In Koala window, select "call"->"H 323".

You will get a "Call H. 323" window.

In the "H323 Address" column, write "85723@198.129.252.168".
This is the example for the 85QCD (where 85723 corresponds to 85QCD)

Click the phone-shape button near the top left of the same window.
A new window "Viveo" will start.

If you are the first and have to set up PIN, use the panel on the right side of the "Call H. 323" window.