Click on "Forum Profile" or "Account Settings" under your name at upper right of the screen (assuming you are on a desktop). There you can change your display name and password.
I recommend you do NOT try to change your login name though, assuming that's even possible in the latest update. SMF (the forum software) tends to muck up accounts when a login name change attempt is made, and you won't be able to get back in without creating an all new account.