how to add cdn link in 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 }}