1. Access to one WordPress.com account or Create one.
2.Click + ‘Add New Site’ at your left side
3.Insert your WordPress site url at the field provided at right (Add an existing WordPress site with Jetpack)
4.Add site username and password
5.Click install Jetpack or you can install the jetpack plugin manually
6.Scroll down the page and Click the button of ‘Start with free’
Done! You can manage the website now.