Open the terminal, and run it this way:

python cellular_automaton.py

Ctrl + C to quit (yes I'm lazy)

If you want to user another ruleset or initial state, change line 60 of cellular_automaton.py:

automaton   = CellularAutomaton (width, height, BIRTH, SURVIVAL, INITIAL_STATE)

where BIRTH and SURVIVAL are lists of integers, and INITIAL_STATE is the filename.

If the game crashes unexpectedly, feel free to send me a mail at 
alexis.vallet@gmail.com with a description of the crash and a stack trace.

Have fun :) !
