To change your username or password, you will need to first log in to your account. If you cannot log in to your account, you'll need to follow the procedure to reset your login credentials outlined in this support article.
To change your username and/or password, you will need to uncheck the box(es) that says "I don't want to change my....." next to the corresponding item that you want to change. This will allow the change fields to display where you can enter your new desired username and/or password.
Current Username & Password
To change your username or password, you must know your current username and password. If you do not know your current username and/or password and just happen to be logged in from a previous session, you will need to log out and use the forgotten username/password option to recover your credentials.