If you wish to change your username, you'll first need to login to your profile.
1. Click on the menu icon on the top right of the page (to the right of your picture), click on Settings, then Account Settings, then the word 'change' to the right of 'username'.
2. Under My account settings click change next to Username to update this information. Your username can not be in use by another member, or contain any spaces or special characters (#*&%!).
3. Type in the new username you wish to use. You'll need to input your password before the change can take effect. Click change username when you're done.