Client Settings is where you are able to manually specify the remote server ip you wish to connect to. To get to the Client Settings, click on the Net Settings button at the bottom of the program, then clicking on the Client Settings button, as seen here:
Once the Client Settings button has been clicked, you should see something similar to the image on the right. In the first edit box, you must specify the server ip or hostname that you wish to connect to (eg. tetrinet.org). In the second edit box, you must enter the nickname you wish to use. Finally, in the drop down box, you must select the Client Mode, or the protocol, that the server you wish to connect to responds to. Once you have done these steps, it is time to connect to the server by clicking on the Connect button. Upon connection, the button will change to read Disconnect. Simply click on this button when you wish to leave the server. Upon connection to a server, you should proceed to the Partyline.