Welcome and Login
Homepage and Root
Login to MailChimp.
Go to Lists -> "Your List" -> Signup forms -> Embedded forms
You will be defaulted to the Classic form. On the right, under "Copy/paste onto your site," there will be a <form action="......"
Copy everything between the action quotes. It will look like this: //xxxxxxxx.us3.list-manage.com/subscribe/post?u=2fa4abd74eab05fce1497c5c5&id=f1c4f782a0
Paste into the MailChimp field on your site