How to override supersized.shutter.css I'm not the best in php manipulation that's why I'm asking. 

function supersized_libraries_info() {
  $libraries['supersized'] = array(
    'title' =&gt; 'Supersized',
    'website' =&gt; 'http://www.buildinternet.com/project/supersized/',
    'download url' =&gt; 'https://github.com/f3ndot/supersized/tree/3718ae83f0945e327cc09530b959c5a8b049871f',
    'version arguments' =&gt; array(
      'file' =&gt; 'slideshow/js/supersized.3.2.8.min.js',
      'pattern' =&gt; '/Version : (\d+)/',
      'lines' =&gt; 4,
    ),
    'files' =&gt; array(
      'js' =&gt; array(
        'slideshow/js/jquery.easing.min.js',
        'slideshow/js/supersized.3.2.8.min.js',
        'slideshow/theme/supersized.shutter.min.js',
      ),
      'css' =&gt; array(
        'slideshow/theme/supersized.shutter.css',
        'slideshow/css/supersized.css',
      ),
    ),
  );
  return $libraries;
}


That's the all code of supersized_libraries_info() function. I wan't to hook that using hook system so for my theme it suppost to be
mytheme_supersized_libraries_info() right?

Then I wan't to just edit css location so that supersized.shutter.css will be in placed in my theme location.

(My code!)

function koko_supersized_libraries_info($variables) {
  $libraries['supersized'] = array(
    'files' =&gt; array(
        'css' =&gt; array(
        path_to_theme() + '/css/supersized.shutter.css',
        'slideshow/css/supersized.css',
      ),
    ),
  );


I just want to edit the css property of that object. I don't know how to get to there.
Mine edit just doesn't work at all (nothing happends).

I want to clear css array and then set mine values.
To alter the value returned from an implementation of hook_libraries_info(), a module or a theme needs to implement hook_libraries_info_alter(). As with other alter hooks, there isn't a way to override the value returned from a specific module, so the hook name is the usual one: modulename_library_info_alter() or themename_library_info_alter().

As side note, you code contains also an error: The parameter is $variables, but the code is using $libraries.