It's a multi-dimensional array, you could first populate him, by asking the user, or just generating instead one random number, two random numbers, like this:
Also, it's not difficult to make the game... you need few functions, some of them to see how many neighbours a simple citizen have. The most funny in this game is the rules, this game is used in a lot of researches, really funny.
x = rand()%20+1;
y = rand()%20+1;
colony[x][y] = '*';
Remember, you don't fill all the array in the first time, just add some citizens and see the evolution.