Please Explain Simple Sitemap for Multisite

I have installed Simple Sitemap for Multisite, added code to .htacess and wp-config files as per usage instructions, but I don't know how this works.

You say: "You can check that your sitemaps have been created by going to: blog.domain.tld/sitemap.xml." I have tried several variations of this URL to suit my site but get a 'page not found' for all of them.

When I go into my FTP I find my old sitemap.xml there which doesn't include the pages in my sub-domains, which is why I installed this plugin.

Where do I find the sitemap that has been created using FTP?
Does it include my sub-domains?
Can I edit it?

Thank you.