The video box can be enabled with the class “video” preceded by a href attribute with the video url.

You can use the following markup in order to build this element:

<div class="dm__videoPlayer-container">
  <img src="./images/your-video-box-image" />

  <div class="dm__videoPlayer-bg--overlay">
  </div> 
  <div class="dm__videoPlayer-caption">
    <div class="dm__iconbox">
      <a class="video" href="your_video_url">
        <span class="dm__iconbox-icon dm__videoPlayer-icon dm__iconbox--circle dm__iconbox--circle icon-play"></span>
      </a> 
    </div><!--/.dm__iconbox -->
  </div><!--/.dm__videoPlayer-caption -->
</div><!--/.dm__videoPlayer-container -->