How/if can use a robots.txt
Here is my site Read-Only: LINK
(how to share your site Read-Only link)
You can configure it in site settings on any hosted site. You’ll find the protocol online on how to write it.
In general, it’s useless on Webflow sites, because there are no dynamic feeds/apis to block bots from. Also no real SEO advantage… bots are controlled by robots.txt, but SEO is not. Better to learn how to use META noindex tags if you’re trying to prevent Google from including specific pages in their SERPs.