Portfolio section is made by most popular jquery Isotope Plugin To add more portfolio items you just need to add following codes
<div class="col-xs-12 col-sm-6 col-md-4 Photoshop Illustrator">
<figure class="works-item">
<img src="img/works/1.jpg" alt="">
<div class="overlay"></div>
<figcaption class="works-inner">
<h4>Project Name</h4>
<p>Illustration, Digital Art</p>
</figcaption>
</figure>
</div>
In here “Photoshop Illustrator” is the class which indicatte filters menu . This class are for the filtering