Need help with sitemap file

No, you send the sitemap to Google (you add it in Webmastertools by Google). If you use the dynamic Bubble.io sitemap it updates automatic. See this post: [New Feature] Dynamic Sitemaps - Announcements / New features - Bubble Forum

Edit: If you want to create a manual sitemap file, you can upload it there in the rootfiles. But there is no need for it.