Making Posts/Blog Entries align/flush left

Do not edit the Twenty Fourteen theme. It is the current default WordPress theme and having access to an original, unedited, copy of the theme is vital in many situations. First create a child theme for your changes. Or install a custom CSS plugin.

In that case, try using Firefox with the Firebug add-on for this kind of CSS troubleshooting. Or use whatever developer tool is available in your web browser.