Unlike ZIP, the RAR modules are not installed with the default installation of OSX so you will need to download the latest version from the RARlabs website.
Once you have downloaded the relevant file to your ‘Downloads’ extract them, once this has been done you will need to open a ‘Terminal’ window and make sure that you are in the directory that host all the files that you have extracted.
To install the needed files to the correct directory, copy the text below into your Terminal window and hit ‘Return’:
sudo install -c -o $USER unrar /usr/local/bin
sudo install -c -o $USER rar /usr/local/bin
unrar x /path/to/file.part01.rar