How to install on Mac
https://ttlc.intuit.com/community/installing/help/how-do-i-install-the-turbotax-software-for-mac/00/26067
How to install Turbo Tax on Windows
https://ttlc.intuit.com/community/refund-status/help/how-do-i-install-the-turbotax-software-for-windows/00/25934
Have you already downloaded it? Access your downloads here
https://shop.turbotax.intuit.com/commerce/account/secure/login.jsp?pagecontext=download
How to download your software purchase
https://ttlc.intuit.com/community/installing/help/how-do-i-download-the-software-i-purchased-at-turbotax-com/00/26075
with windows (won't install on a MAC or a Windows OS below 8.1) just double click the downloaded file.