How to fix locomotive.js uncaught reference error?

Question

I want to use locomotive.js on my project and have installed it on vscode (npm install locomotive-scroll) and have even followed this tutorial:

https://www.youtube.com/watch?v=zrM6N-G6U_M&list=PLNf1MNtmy_vyQkFjuNqxKpQT0U_rbC_y8&index=19

My problem is that I get an error saying:

Uncaught SyntaxError: Cannot use import statement outside a module

I have no idea what to do. I have done some research on compilers and stuff like that but I don't think the tutorial mentioned any of that. It was literally: install, copy, paste and you're good to go.

Here's the script:

import LocomotiveScroll from 'locomotive-scroll';

const scroll = new LocomotiveScroll({
    el: document.querySelector('[data-scroll-container]'),
    smooth: true
});

and to link it to my html:

<script src="index.js"></script>

Any help or ideas would be appreciated.