You can change your registered e-mail address and password from the Settings item in the menu at the top of the page after logging in.
Change your e-mail address here.
Change your password here.
You can use 6 to 72 digits that include alphanumeric characters (a-zA-Z0-9) and symbols (=+*:;!|$&%#@~.,?_"&#'(){}[]<>^/\) for your password.