1. Unpack the downloaded file: 
    bunzip2 -c polymake-VERSION.tar.bz2 | tar xfp -
    It will create a directory tree polymake-VERSION. Change into it: 
    cd polymake-VERSION
  2. Check the system requirements and proceed with the configuration and build steps as described in the installation instructions. You can also switch to the offline mode now and read the local copy of the installation instructions contained in the source distribution.