WELLS template | Help with custom CSS

Site URL: https://wells-demo.squarespace.com/blog-wells

Hi there. I am using the WELLS template, and I want to know how to make the content next to the sidebar 100% width. The photo galleries, like the home and this page and perfect examples of what I am after, yet when I create other pages and add blocks, the content has a fixed width; for example, take a look at this page or this one. 

I contacted the Squarespace support team, and they told me that I should post on this forum to get help with custom CSS, as it is impossible to make those content 100% with the customization options that come with the template. For example, I'd love to use a hero image, 100% width across all viewports, on a blank page, with a text below, among other things.

Can someone help me? Also willing to hire a developer to customize my site with these requirements if someone is interested. 

I appreciate any help you can provide.
Flo

Hi Flo,

You can set the site width to maximum wich is 1800 pixels.

Got to DESIGN>STYLE>Site Wide options
On most laptops it will display on the whole width.

Antoine