To add a new slider item copy/paste a list item and set image source.
<ul class="slides header-carousel"> <li><img src="images/carouselItem1.jpg" alt=""></li> <li><img src="images/carouselItem2.jpg" alt=""></li> <li><img src="images/carouselItem3.jpg" alt=""></li> <li><img src="images/carouselItem4.jpg" alt=""></li> </ul>