Just enter your full sitemap URL (with http or https) and click submit.

Upon successful submission, you will see a message like this:

Sitemap Notification Received

Your Sitemap has been successfully added to our list of Sitemaps to crawl. If this is the first time you are notifying Google about this Sitemap, please add it via http://www.google.com/webmasters/tools/ so you can track its status. Please note that we do not add all submitted URLs to our index, and we cannot make any predictions or guarantees about when or if they will appear.

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I am adding new codes and experiments to it.