background height

Is there any CSS code that can be used to define the height of the background of the box of the area dedicated to the sign up box? In the theme that I am using the background area of this plugin is supposed to match up with other things on the page and the height of the background is falling short. I could easily measure the height needed if I knew the CSS code to define it. I would include the link but we have a construction page up as the site has not yet launched. Any help is greatly appreciated. Thank you.

https://ww.wp.xz.cn/plugins/genesis-enews-extended/