Hi Charles,
Thank you for reaching out to us. To d this simply add the following code in the Theme Options > CSS:
.entry-wrap {
background-color: #2c2c2c;
box-shadow: inset 0 -0.125em 0.5em 0 rgb(44, 44, 44), 0 3px 2px -2px rgb(44, 44, 44);
}
If you would like to learn CSS, I am sharing few resources that you take a look to get started with CSS and an interesting tool that you can use to speed up the development process.
I recommend you to watch following video that will help you to get started with CSS.
https://www.youtube.com/watch?v=MFR4WXiLzpc
Sometimes it can get a bit difficult to find out the right selector to be able to write the required CSS codes. A handy tool that can help you in this is Google Chrome dev tools. I am sharing the resource that you can refer to get started with dev tools.
https://developers.google.com/web/tools/chrome-devtools/css/
https://developers.google.com/web/tools/chrome-devtools/
https://www.youtube.com/watch?v=tP_kXBJWPhQ&t=200s
Hope this helps!