want to quit.. but I am not sure who I talk to..

One has to do what makes them happy in life, you should have learned that by now being a nurse. Life is too short! Besides do you really care what they think? I mean really, unless your mother or best friend works there I wouldn't give it a second thought. People come and go all the time and management is used to this.

Notify your manager verbally if at all humanly possible and in writing (but wait until it's 2 or 3 weeks before you want to leave, it would be a mistake to give this much notice and besides you are under no obligation to give more). Keep a copy of your letter.

One thing, you do not owe them any explanations and don't apologize! We women are terrible about doing that(myself included)! If they try to really pin you down for a reason for your resignation then just explain that psych nursing is your calling. That should make them back off pretty quick because most of us really don't like working with psych patients but have great respect for those who do.

Date the letter, address it to your manager, and simply state that your last day of work will be such and such date. If you want you can thank them for new learning experiences that you've gained while in their employ.

Hospitals are run like the military in many ways. Stick with the chain of command by notifying your manager first, then you can tell the others. Besides they are charge nurses and can not officially (though some might like to think the can) discipline, hire, or fire anyone (or except resignations).

Good luck. I've been there and I do emphasize with you.