It wasn’t clear to me that you were talking about that specific implementation. So I thought you just had a general HowTo question, but however way is that same.
When using third party addons, usually you get files and scripts(like .js) from them and you place in your website and some may provide you link to their CDN link.
In Webflow we do same thing; we upload media files on Assets and for scripts you places them on Custom code fields. Since for custom code you get input fields, you should know that you can copy paste those JS scripts there. You may also know that JS code should be wrapped around <script></script>
There is not much to see here because JS is implemented on the Project settings. So check the live link here https://works-by-abi-rana.webflow.io/, you can check the source code in the browser.
So what I did was:
Copy/paste bug-min.js code in the Project settings > Custom code
Upload those to images provided with the source (fly-sprite.png and spider-sprite.png)
And at last you should initiate the function like below, this should be below the bug-min.js code
new BugController({
imageSprite: 'path/to/fly-sprite.png'
});
new SpiderController({
imageSprite: 'path/to/spider-sprite.png'
});