Click on "User Control Panel" near the top left corner of your screen, then click on the profile tab. Then click on ‘edit account settings’ on the left.
To change you password, type in your new password in both the 'New password' and 'Confirm password' boxes. Then type in your old/current password in the 'Current password' box. Click "submit", and you're done! Make sure you remember your new password and use it to log in to the forums and game next time.
To change your e-mail address, type in your new e-mail address in both the 'E-mail address' and 'Confirm e-mail address' boxes. Then type in your current password in the 'Current password' box. Click "submit". You'll receive an e-mail explaining that your account has been deactivated. You will need to wait for an administrator to re-activate your account, at which point your new e-mail address will be associated with your account.