Generally we log in our Facebook account with our e-mail address. You can set a username in your Facebook account and you can log in your Facebook account by this username. After set a username everybody can find you easily in Facebook with your username. With a username you will get a profile URL like as www.facebook.com/your_username. So it’ll be very easy to find your Facebook account by username. Let’s start how you can set a username in your Facebook account.
Sort Instruction: Log in> Setting > General Setting> Username>Save changes.
You can see the images for better understand.