1. In order to our JavaScript changes to take effect we have to change the script included at the end of your HTML file to 'js/index' instead of 'js/index.min' like shown in the screenshot.
2. Include the fancybox plugin into the theme's directory. Download Fancybox and include the 'jquery.fancybox.pack.js' into 'js/libs/' folder. You don't have to include the Facybox' css code as it's already included in Odiss.
3. Define the 'fancybox' as a module within the 'js/index.js' file, set the path to the plugin and the dependencies, like shown in the screenshot.
4. Open the JavaScript file where you want to initialize / use FancyBox.
5. Require for 'fancybox' as shown in the screenshot.
6. Once that's done, you should be able to use FancyBox / third party lib within this JavaScript file.