How do I submit a letter of resignation?

I'm very new to the world of working that doesnt involve just texting a supervisor that I'm not returning. I have PTO hours at this job and am going to check what happens to them. I want to leave on good terms and dont know how to word my letter nor who to submit it to. I've been here for almost a year and wanted to ask for a letter of recommendation but am already nervous about resigning. Thank you.

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