Hello,
To apply any sort of Custom CSS to any specific Page then most commonly their Page ID or Page Class is used which is dynamically generated under the body tag of that Page which you can check through the browser Inspect tool.
So, we have applied the following Custom CSS on your Site to make the Shop page max-width 1600px:
.archive .website-wrapper .main-page-wrapper .container {
max-width: 1600px !important;
}
In thi CSS, the .archive is the Shop page class name and as the container was under the main page wrapper so it needs to be accessed through the hierarchy under the CSS.
Location to find Custom CSS, go to Dashboard >> Theme Settings >> Custom CSS >> Global CSS section >> at the bottom you can the CSS pasted.
Please check back your Site after completely clearing browser and server cache.
Best Regards
.
