If you are not satisfied with your selected facebook username or facebook profile URL then there is a good news for you. Facebook is giving you one more chance to finalise your facebook username. Once you change your facebook username you can’t switch back to the previous one, so make changes carefully.
Here is what you have to do to change your facebook username: Click on the “Settings” tab and you will find a “Username” tab there. Now click on “change” to select new username, check its availibility and if its available you can get that username instantly.