(NOTE: You cannot change your account information from the mobile apps at this time.)
Select My Account from under your username at the top right of the page.
To Change your Username or Email:
From the Contact Info tab, enter your new username and/or e-mail address. (From this tab, you may also update your name and add a profile picture.)
Be sure to click Update Info to save changes.
To Change your Password:
Select the Password tab.
Enter your current password and new password then click Change Password to confirm.
(NOTE: If you do not know your current password, see Recover password or username.)