Go to Plugins > Add new. Now search for "Jetpack". In the search results page find the plugin called "Jetpack by WordPress.com". Now click on Install Now.
After installation is done click on Activate Plugin. Now you'll see a green button that says "Connect to WordPress.com". Now you have to login to your WordPress.com account (different from WordPress.org). If you don't have an account yet, create one.
Then click on Authorize Jetpack. Now hover over Jetpack in the sidebar and click on Site Stats.