Hello,
Thank you for contacting us.
To make the newsletter section styled as our demo variant, you need to place the form code into the block with class: et-mailchimp (see the screenshot) https://gyazo.com/1d9e038fbce14bfdadcbd451b203002b
This was made so the xstore styles do not conflict with Mailchimp styles. And so you may have the opportunity to use different plugin skins. If you need to change the form styles you may always write your own css in custom css area in Theme Settings.
Regards















