Quitting job at Mcdonalds?

I have been working at Mcdonalds a little over a month now, and its simply time for me to leave. I hate working there, and not only that, I have to return to my college in a different city very soon. Every day I leave with a pounding headache. And like I said before school is approaching. Now the problem is, I didnt give them a two week notice and it is way too late for one. I dont know why I didnt. How do I go about quitting and wat do I say?