I know nothing in JS but sometimes I succeed using snippets I find on sites like Codepen. Most of the time I miserably fail.
There's HTML code, that you can try to reproduce in Webflow: most likely, it's giving the right classname for the right element. You don't want to just use the weblfow HTML Code widget because you'll lose the ability to style these elements in Webflow too.
There's CSS code that you can either add as custom code in your site dashboard, or reproduce within webflow if you know how to translate CSS code to Webflow UI (it's easy, it's the same vocabulary), or a mix of both.
There's JS that you have no choice than to add as custom code, either in the site dashboard custom code zone (code will be placed in the head of all the pages of the site) or in the page itself with the HTML code widget, so it appears in the HTML body of the page. JS scripts usually require a specific place to work or work well: either in the head, or at the beginning of the body, or the end of the body.
That's pretty much all I know and most of the time it's not enough (: The real thing I miss is not being able to use the browser inspector to debug JS, so when it doesn't work, I can't do anything.