To include an external package in a [[Google Apps Script]] file that is not a web app you can use the eval function to read the script into the namespace.
```javascript
eval(UrlFetchApp.fetch("https://unpkg.com/h3-js").getContentText());
```
In a [[web app]], you can easily include external JavaScript files by importing the script from CDN.
```html
<script src="https://unpkg.com/h3-js"></script>
```