How to change content area width in blog post?

I’m using Simply theme for my blog. I would like to make the width for my posts to be a bit wider.
I know it’s possible by changing it in CSS or using Code Injection.
But I can’t figure it out.
I’ve included a screenshot of what I wanted to do

Can you share a link to your site? Or to the theme?

Also, while you might want to make the post width wider, it’s likely optimized for the ideal line length. Here’s a great overview of line length: Line length | Butterick’s Practical Typography

@TheRoyalFig This is my blog post link. Exposing Kubernetes services with MetalLB and Nginx ingress controller

Hi, I’m having the same problem using EDITION theme.
I tried to modify the Header code under Settings > Code Injection > Site Header like this:

<link rel="stylesheet" href="" integrity="sha512-+oRH6u1nDGSm3hH8poU85YFIVTdSnS2f+texdPGrURaJh8hzmhMiZrQth6l56P4ZQmxeZzd2DqVEMqQoJ8J89A==" crossorigin="anonymous" referrerpolicy="no-referrer" />

    .gh-head-menu .nav-twitter a {
        font-size: 0 !important;

    .gh-head-menu .nav-twitter a::before {
        font-family: "Font Awesome 6 Brands";
        display: inline-block;
        font-size: 20px;
        font-style: normal;
        font-weight: normal;
        font-variant: normal;
        text-rendering: auto;
        -webkit-font-smoothing: antialiased;

    .gh-head-menu .nav-twitter a::before {content: "\f099"}
 	@media (min-width: 992px) {
	  .col-lg-6 {
	    flex: 0 0 85% !important;
 	   max-width: 85% !important;

with no luck.

Note the @media part. I took that suggestion from

Can anyone help me out?