Leaving a job after the first two weeks, trying to figure out how to do it

Sorry in advance if the post seems scattered.

I just started a new job about two weeks ago and it is starting to sent in that it isn't for me. I thought it was new job jitters since it is a new enviroment but it isn't the case. (I'm about to see my manager from my past position this Friday. I left on a good note so it is likely that I will get it again.)

I need to know what is the best way to resign. I haven't left a position this early before so I'm unsure on how to do it. It's a part time job; I don't know how formal I should be. Should I write a two weeks notice despite still being in the training phase or tell the manager in person?

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