Where did you download your client? This version (NA version) is available for download in the homepage or you can alternatively click here: https://download.gamigo.com/FiestaOnlineDownloader_US.exe
There are some other Fiesta versions that are language specific such as German, Spanish and French... NA one is in english language.
We have a total of 4 servers available to play: Isya, Pagel, Jenira, Enid - Isya is the highest populated so if you log there is guaranteed that you will find other players around.
I'm not sure why you do see only one server available to select but maybe you've got an incorrect client? What is the name of the server you see available?