Your site comes with two built-in URLs for your sitemap in both txt and XML formats.
(TXT format) https://yourfreedomain.findiss.com/custom_sitemap.txt
or
(XML format) https://yourfreedomain.findiss.com/custom_sitemap.xml
NOTE: if you are using your custom domain, change it will be under:
(TXT format) https://www.yourdomain.com/custom_sitemap.txt
or
(XML format) https://www.yourfreedomain.findiss.com/custom_sitemap.xml