Facebook allows you to create a username or change it to a new one if the username of your choice is still available. Facebook usernames are handy when you are sharing your Facebook Profile URL to a friend and is asking him/her to add you. A sample Facebook Profile URL would look like facebook.com/<your-username>
Here are the steps to change the same.
2. Go to Account (on top right) -> Select “Account Settings“.
3. Scroll down to “Username” section and click on “Change“.
4. Enter your new username and click on “Check Availability“. You will be able to save the username if it’s still available.
Note: You can only change your username once.
If you have exceeded the username limit, please visit Facebook Help Center. http://www.facebook.com/help/search/?q=username.