How to Create a Content Container

Hey there, using the theme “Lifestyle” here, very simple. I’m wondering how I’d go about creating a container that would include the content of my pages.

My page is under construction, but here is an idea of the template: https://wordpress.org/themes/lifestyle/

I’ve changed the color of the body, and would like the container to be white and contain all the content (from the bottom of the slider and down). I hope that makes sense.

I was able to change the color of the entire container, which extends to the top of the page…but I’d like to limit where the section is. I’d also like to add some padding on the sides. So far I have:

div.site-container {
background-color:white;
}

I’ve tried a few things, doesn’t seem to be working for me. Thanks so much for any info!