Well, it's just a keystroke, so you get it by doing a getc, or a (sys)read. Of course, you might be using a terminal that gets to ^C first - but then your problem is "how to disable the terminal from intercepting ^C". In that case (for Unix terminals), stty is your friend.

Now, in case your real question is "how do I intercept SIGINT", see the answer elsewhere in this thread. But note that that answer isn't about capturing ^C - merely its effect on some terminals.