To sign up for Gmail, create a Gmail account on Google. You can use your username and password to log in to other Google products like YouTube, Google Play, and Google Drive.
Go to the Google Account signup page,
Follow the steps to set up your account in the above link
Use the account you used to sign in to Gmail.
The account with the username I want is already has taken by someone. You cannot get a specific Gmail address if the username you requested is already in use.
Very close to the real username (for example, if firstname.lastname@example.org already exists, you cannot use email@example.com).
When the username used by someone in the past has been deleted, Google will reserve it to avoid spam or misuse.