When you click on the "Add" button in the "Echoserver" tab, you will see a
window and a popup as shown here:

In the "Login Info" popup, simply provide the information about the echoServer
you are going to use to connect with your partners.

If you don't yet have one, Echogent Systems is sponsoring a "demo echoServer"
you can try out. Here are the connection details for it:

As for what UserID to put into the popup, either put in there what your
echoServer admin has reserved for you, or choose a "Partner ID" for yourself
that other EchoVNC users should use when they connect to you. For example,
you could use "OfficeComputer", or "Mom's Laptop", etc. And the easier it is
to spell correctly, the less difficulty your EchoVNC partners will have in
correctly connecting with you.