The Jetpack plugin requires you to connect to a WordPress.com account to be fully activated.
To do so, you will have to create a WordPress.com account here:
If you had previously created an account, but forgot the password, you can request a new password by entering your email address here:
Please follow the instructions carefully. You'll receive an email during the reset process, so make sure you read it for important instructions. If you don't receive the email right away, check your spam folders as well. The confirmation email can get caught in them sometimes.
Please note that WordPress.com accounts are different from the account you use to administrate your blog. WordPress.com and self-hosted blogs available through WordPress.org are two different entities.
Please check out the following links to learn the differences.