How do I add custom code to my feed?

On Shopify 2.0 themes, you can use the Custom HTML code box on the Instafeed app extension to add your own code on top of Instafeed:

Custom HTML empty box on the Instafeed app extension.

Besides HTML, you can also add CSS and JavaScript code.

CSS

To add CSS code, simply put it inside style tags.

To add JavaScript code, simply put it inside script tags. Instafeed fires an onload event that you can use to implement custom code.