From the official download page:
Dependencies (debian/ubuntu package names):
WxWidgets GTK 2.8 (libwxgtk2.8-dev)
Unpack the archive and run ./gct-game-startup from a proper directory.
Run install.sh as a root (e.g. sudo ./install.sh) to install the game. Afterwards, every user will be able to run gct-game-startup command.
Startup doesn't kill server, so kill it manually if you have to with: killall gct-server
Run ./gct-server for dedicated server. It doesn't need any libraries related to the graphics, so can be run on almost every modern Linux, even without X11.
If the install doesn't add it to the launcher, just do it manually :)