Before doing this,let us know what are sitemaps and how they will help us.
The reason we use them is,they will help google bot to crawl,index pages of your site and tell you if there are any problems when they try to index it.
It also helps you to know,how many pages exactly are indexed,and what people searched [keywords] in the search engine get to your web-blog
Add your blog url(eg: widgetblogger.co.cc).Don't add with http or www.
5.Copy the metatag.
Now,sign into your blogger account>click the layout button>Edit html and paste the metatag just after the head tag and save the changes.
and click the verify button in the google webmaster tools and there will be a confirmation message saying that you have sucessfully verified.
Go back to the google webmaster dashboard or (home) and click the 'Add' link which is next to your blog name and in the Sitemaps column.Then,you do this,
Choose 'Add general web sitemap' from the dropdown menu and type rss.xml or atom.xml next to your blog address as shown below
and click the 'Add General Web Sitemap' button.
6.That's it.Now your sitemap is successfully submitted to google.Check 2 or 3 days after and you will see the detailed statistics of your blog(indexed pages,any errors,etc.)