This is where you add your game servers - this allows your game servers to talk to your dashboard and all other GST services. The amount of servers you can add depends on your subscription and the number of servers you have selected. More info on that can be found here
Once you have added your first server you will see it will be added to the list of servers. Clicking on the server will show extra fields.
Here you will see the information you have just entered as well as the option to add your RCON details. Enter your RCON port and RCON password and click update. Your server will then be able to access GST services.