Widening Section Containers

[graceapollock]

Hi guys- I've been struggling because my shopify theme (Envy) has a container over my entire site that prevents sections from being full width. I don't want to mess around with removing the container from the theme entirely, but certain sections I really want to widen. 

Here's what is looks like. The site is stablefeed.com

Does anyone have experience customizing this, either in the custom CSS on the product page editor, or within the code? I don't have much experience coding, so any guidance is greatly appreciated!