[Customizr] How to reduce post width without sidebars

Hi,

I’d like to reduce the width of the pages but I have been unable to find a code to do this.

I am only able to access the custom css in the wordpress theme and not the whole page files so would be looking for a snippet.

Would anybody be able to advise on this?

I thought one way of doing this, would be to remove the content from the right side bar.

Thank you

C F