As Caarrie says, you need to have downloaded the PlaneShift_CBV0.3.020-x64.bin file with your torrent client first (or used a direct link if you don't have a torrent client set up).
One you have downloaded the .bin file open a terminal and do the following: (don't type the ?>)
?> cd /location/of/PlaneShift_CBV0.3.020-x64.bin
?> ls *.bin
this should show you
PlaneShift_CBV0.3.020-x64.bin
or similar. this checks that you are in the same directory as the installer.
?> chmod +x PlaneShift*
to make the downloaded executable so that you can run it to install the game.
?> ./PlaneShift_CBV0.3.020-x64.bin
to run the installer.
*Note* if the downloaded file is not called PlaneShift_CBV0.3.020-x64.bin then substitute the correct name in all the above.
The installer will ask you where to install to as well. You are probably best to run the installer with your own account and install somewhere into your home directory (e.g. /home/doanster/games/ - create the directory first if it does not exist) this will mean that you can play the game without changing any permissions or other things.
If you want to install it so that users other that you can play you will need to install as the root user and do a system wide install.
Simply do
?> su -
as the first command and select a location like /usr/local/games/ as the install directory (again, create it if it does not exist). You will need to add all the users that you want to be able to play the game (including your own) to the 'games' group and log out and log back in again. (No need to restart, just log out & in)
Good luck