Comment ajouter un lien CDN dans Shopify

If you just want to load everything so it works, add this code in the head of 
Admin > Themes > Template Editor > theme.liquid

Make sure to paste the code in-between the <head> </head> tags.

you can try to load them as the snippet bellow :

{{ '//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js' | script_tag }}
{{ '//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css' | stylesheet_tag }}
{{ '//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css' | stylesheet_tag }}
Lokesh003