what theme?

[DELETED]

You may need to adjust the margins within the surrounding divs to suit your taste, but right now the entry header and content are set to display at only 68.9% of the entire column width.

It might help if you provided the theme and site link =d

You just need to edit the CSS, or stylesheet for the theme. Located in the them files folder. Should be style.css

You can edit it from the dashboard, just make sure to have a back up copy before you start making changes.