Only one Software Token can be registered to a single SQUARE ENIX account. If you wish to register multiple Software Tokens, you must either prepare a secondary device and register a Software Token app for each account, or purchase a Security Token (keychain type) separately.

Please visit the following page for more information on how to register a Software Token.
http://support.na.square-enix.com/faqarticle.php?kid=66681&id=496&la=1&ret=faq&pv=100&page=0&c=0&sc=0&so=4