What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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I'm sorry but I don't fully understand your question.
Could you please clarify it a bit more?
Do you want to set a custom email address for your email notifications as described on this guide: https://www.jotform.com/help/238-How-to-Add-a-Custom-Sender-Address-to-an-Email-Alert?
If this is correct, I think that you're referring to the verification code. This code will be sent to you in an email, you need to check your email (the account that you're setting to be the new sender) and look for the verification code and paste it in the Verification Code textbox on the wizard (see step 6 on the mentioned guide).
Please let us know if this helps.