Go to admin panel, Then Extensions → Templates. Select the template → select option tab → Then select layouts. By default Layouts will select default layout.
You need to select your layout override first because layout override depend page layout setting.
Select your layout which you want to change layout width (because layouts only affected with selected layout override. For more information: https://bdthemes.com/support/knowledge-base/understanding-about-layout-of-warp-framework/)
By default full width layout width will be selected, if you want boxed width layout so you need to select Boxed from below dropdown.
Then click save and close button for save your settings.