Linking to current signup field

OK, I think I know what I’m talking about now. Thanks for your patience with me.

We have a current Constant Contact signup field and we want to live the design and layout as is. How do I connect this form to the current singup field? Would I update the link info in my header.php?

Thanks again for your time.
dk

http://wordpress.org/extend/plugins/constant-contact-api/