Once your blog is verified you can add sitemaps for your blog[From the Left Pane > Site Configuration > Sitemap].In the sitemap url give the following url as shown in this screenshot and click the Submit Sitemap button
If you have more than 100 posts on your blog, then add an additional sitemap url
If your blog has more than 200 posts, then add one more sitemap url
If it has more than 300 posts, then add one more sitemap
Continue this process depending upon the number of posts on your blog. So this means that you will be adding additional sitemaps for every 100 posts.
Once you have added the Sitemap, you can play around with the different other tools in GWT. It will provide you with a better analysis your site, show you the sites linking to you, help you in managing your site links and much more.