As an ordinary users here in our community we can not change our own username or let say display name and only admin can do that but if you want to change your name you can leave a private message to our admin theymos but I don't think  that you will be given a chance  but just give a try. Anyways like what other said above only thing you can do is to create another account cause your account is still newbie yet if you don't want that username then you can create another one.