Looking to access your theme's code or language options with Shopify's new theme editor layout?
In your Shopify admin click on Online store > Themes
Next to the theme that you want to edit click on the Menu button which is a small square with 3 blue dots
This will open a submenu of options which includes: Edit HTMl / CSS and Edit Language
To get your access token go to:
Once you have this token open your Customize theme page and add this token to the instagram feed section and click save.