Design/Adding custom CSS/JS
From Shopnix Help
What is Adding custom CSS / JS ?
You can customize your existing shopnix store using HTML, CSS and JS . You can do the same by using 2 approaches.
The first one is to create an HTML widget from ADMIN > SETUP > WIDGETS. Here you can create HTML blocks that you want to be placed on your side and associate styling with it as per your requirement.
The second apporach is to directly edit the code from ADMIN > SETUP > PAGES > FOOTER/HEADER. Using this page, you can either write custom html/css/js code or modify existing site elements using JS/CSS. You'll find example code already in place here for your reference.