With Windows 10S the "S" stands for Secure. That particular version can only install programs and software obtained directly from the MicroSoft Store, and that's it. To change from Windows 10S to regular Windows 10 Home or Windows 10 Professional (whichever you have) follow the guidance at https://support.microsoft.com/en-us/help/4020089/windows-10-in-s-mode-faq for switching out of S-Mode. Once you have done that you'll be able to install TurboTax as well as any other program not purchased directly from the Microsoft store.
