Making all of the content (posts and sidebar_ share background

I have to say, i LOVEEEE this them! It is very easy to customize with my limited knowledge of css and coding with the compliments of google. I was able to merge skins 1 and 3 to make the color scheme the default, but with the dark background, and I was also able to add an extra sidebar to have a widget between the slider and the blog/news posts as well as make another left sidebar page template so two pages can have the left sidebar, but with different widgets

But enough about me bragging about how I was able to customize this (haha this is such a big accomplishment for me! Im sure it would have been nothing for a lot of you on here). I wanted to change the background of the content on the page, just to give more of a seamless look to the content instead of all of the individual boxes.

I’d like for the sidebars and blog posts to share a background. I uploaded a screenshot of my site to show how it looks, and then a screen shot of a totally different site to show what I am trying to achieve.

MY SITE: https://i54.tinypic.com/24xi63n.png
WHAT IM TRYING TO ACHIEVE: https://i55.tinypic.com/fylgdu.png

No idea if the other site uses wordpress (https://CodySimpson.com its the website of a singer signed to Atlanta Records…so I’m sure they’ve hired the most advanced web designers, and programers by the look of the intricacy and the custom widgets), but I want to try to achieve that with my wordpress theme.

I did do a lot of customizing, I guess you could say, but for the most part it was just changing colors…..so the coding for the theme is basically the same as when you first upload it. If someone can just give me a code to input or kind of explain in detail what I can do or need to change to achieve that seamless background…please let me know!