How to change your Facebook Username profile or @ facebook.com E-mail

Facebook launched "usernames" feature in June 2009 made every Facebook user to select a unique username for their profiles and shorten their numbers of desired names Facebook profile addresses. Facebook earlier does not allow users to edit their profile of the user names once they chose but now Facebook have enabled members to change Facebook username only once. In addition, you can also change your email address of Facebook Messages i.e. yourname