Before you install white_dune on macosx, you have to install https://www.xquartz.org/:

To install a .tar.gz file use as normal user ($) in the terminal:

$ gzip -cd file.tar.gz | tar -xvf -

You can also put the tar.gz file in the desktop or home folder and doubleclick to it. Stuffit expander will extract a .app folder, the application.