1) Make sure you have the following libraries properly installed:
   - GTK+ 1.2
     http://www.gtk.org/
     download: ftp://ftp.gtk.org/pub/gtk/v1.2/binary/
   - fftw
     http://www.fftw.org/
     download: http://www.fftw.org/download.html#platformspecific

   On Debian systems, this should do:
   # apt-get install fftw2 fftw-dev libgtk1.2 libgtk1.2-dev

2) $ tar xzf xspectrum-0.1.tgz
   $ cd xspectrum-0.1

3) $ make

4) # make install