Download, untar with the command "tar -zxvf volatility-2.4.tar.gz". Go into the directory created. There may be a configure script. If so, run that as in "./configure". If that succeeds, then next run the make command, and finally "sudo make install" to install it. The default location will be in /usr/local instead of /usr, so /usr/local/bin will need to be in your path environment variable.
Ok. This is a python script. There is a Makefile, and running "make" will put the script and stuff in the build directory. Then if you run "sudo make install" it will put all the stuff in the proper places so you can run vol.py to run it - it is put in /usr/bin/vol.py. There may be missing python modules that you will need to install. In my case, there were several.