Before we start, the best way to understand how this plugin works is the demo.html file included in the zip file. ( open it with any text editor and see the markup by yourself )
1. Download the zip file and extract it.
2. Copy fancyg.min.css from the ely-jquery-gallery/css folder and paste it to your project folder.
3. Copy fancyg.min.js and justifiedGallery.min.js from the ely-jquery-gallery/js folder and paste it to your project folder.
4. Now open your index.html file with your text editor, and paste this code between the <head></head> tag. ( if you are already using jquery, do not copy the script line )
<link rel="stylesheet" href="fancyg.min.css"> <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
5. After that copy this code and paste it before the body closing tag </body>
<script src="justifiedGallery.min.js"></script> <script src="fancyg.min.js"></script>
6. Now, follow the gallery html markup section.