Overriding Hugo Theme Files
In most cases, themes do not exactly match what you want in your site.
For instance, you have an old version of jquery is in the theme:
1/themes/themename/static/js/jquery.min.js
Override it by copying the new version as:
1/static/js/jquery.min.js
So as you may already have figured out by now, you just have to remove the path /themes/themename and that's the override equivalent.
See details in https://bwaycer.github.io/hugo_tutorial.hugo/themes/customizing/