My site uses Twenty Fourteen theme. But the theme is very narrow.
You should open Appearance – Editor menu item and edit
- press Ctrl + F (or Search in menu) and type 1260. It’s the width of the whole site. Replace 1260 with your width in every entry;
- by the same way find 672. It’s the width of content part of your site. Replace;
- mainly. find 474. It’s the max width of text. Replace in every entry.
- press Update file button.