Hello,
1/ Do you use Mailchimp for WordPress plugin to create the form? Do you use WPBakery? Enable WPB for static blocks – https://xstore.helpscoutdocs.com/article/101-wpbakery-page-builder , create Prefooter static block and add it into the desired widget area.
Copy shortcode of form – https://gyazo.com/73b79f130bada3d9966f3f656c5c253f > add into the static block using HTML element
Regards