Mailchimp Integration Help!

I cannot get this integrated correctly. I want people to sign up on my website for an email subscription. Once they sign up I want them to get an email to confirm their sign up. Once they confirm sign up I want them to get another email with a discount code for their first purchase. I have tried every tutorial online I can find and I cannot get this to work! I have tried the send final welcome email function. I have also tried the embedded form. I have also tried an campaign automation. No matter what I do it does not work. I get different errors with each. Can anyone help???

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