title: Which file should I override to change edit form template in Sonata Admin?
body: <p>I follow this tutorial to add a preview of my image file in my sonata admin (symfony3)</p>
  
  <p><a href="http://symfony.com/doc/current/bundles/SonataAdminBundle/cookbook/recipe_image_previews.html" rel="nofollow noreferrer">http://symfony.com/doc/current/bundles/SonataAdminBundle/cookbook/recipe_image_previews.html</a></p>
  
  <p>But I not being able to add the CSS parte. The image is too large.</p>
  
  <p>Should I override one of the sonata templates for it? If yes, which file I change and how do I do it? [I'm pretty new in sonata/symfony3]</p>
  
  <p>If not, how should I add the css file in the project?</p>
  
  <p>My actual code is exactly as the tutorial:</p>
  
  <pre><code>class ImageAdmin extends Admin
  {
      protected function configureFormFields(FormMapper $formMapper)
      {
          // get the current Image instance
          $image = $this-&gt;getSubject();
  
          // use $fileFieldOptions so we can add other options to the field
          $fileFieldOptions = array('required' =&gt; false);
          if ($image &amp;&amp; ($webPath = $image-&gt;getWebPath())) {
              // get the container so the full path to the image can be set
              $container = $this-&gt;getConfigurationPool()-&gt;getContainer();
              $fullPath = $container-&gt;get('request')-&gt;getBasePath().'/'.$webPath;
  
              // add a 'help' option containing the preview's img tag
              $fileFieldOptions['help'] = '&lt;img src="'.$fullPath.'" class="admin-preview" /&gt;';
          }
  
          $formMapper
              // ... other fields ...
              -&gt;add('file', 'file', $fileFieldOptions)
          ;
      }
      // ...
  }
  </code></pre>