you don't need to do anything except use the Google pre-defined syntax to get a blogger/ blogspot blog to have a Sitemap. All you need do is append the url with the following: /sites/feeds/default add that to Google Webmaster tools and Google takes care of the rest
Did you understand what I posted? all blogspot blogs already have a sitemap built in, a blogspot is a Google product, all that is required of you is to take the blogspot blogs RSS feed and enter that feed url into Google Webmaster Tools and you have a sitemap. If you don't know what your blogspot feed url is, that's easy: take your blog url: yourblog dot blogspot dot com and add this to it: /feeds/posts/default that is your blogspot's RSS feed and does double duty as your sitemap url as well. hope that helps
okay... http://YOURBLOG.blogspot.com/feeds/posts/default http://YOURBLOG.blogspot.com/rss.xml both will work all the best