here is very easy way to find it.
For example: www.anjco.blogspot.com is my blog.
here is sitemap url
www.anjco.blogspot.com/atom.xml?redirect=false&start-index=1&max-results=500
For custom domains: www.anjco.com is my blog domain.
here is sitemap url
www.anjco.com/atom.xml?redirect=false&start-index=1&max-results=500
How to submit it on google webmaster.
open the google webmaster tools www.google.com/webmasters/ and add your blog.
click on your site and select the sitemap.
then click on add/test sitemap.
enter " /atom.xml?redirect=false&start-index=1&max-results=500 " there is test it. if showing the number of urls greater then 0 then you can submit it.
