How do I give notice at a Big 4 firm?

How do I give notice at a Big 4 firm? I'm still on probation and I want out. I'm not in accounting, I'm in IT audit. It'll be pretty easy to find another job. I'm not too worried. I see adverts looking for graduate programmers all the time. Ill probably use the money I made here to do some traveling first.

Anyway, I'm just a newbie and don't know how to do this. Do I contact HR? Do I tell my manager first? Do I email the director of my business unit who I supposedly "report to" but barely ever see? Will I have to sit in a meeting with him/her and explain myself? Please respond asap because my probation is nearly up, and I'd rather give my notice before its finished.

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