If the software was purchased from TurboTax you will need to contact TurboTax support so they can push the Mac installation file to your download account at no charge.
TurboTax support is open from 5am to 5pm Pacific time, Monday thru Friday
Use this website to contact TurboTax support during business hours - https://support.turbotax.intuit.com/contact/
Support can also be reached by messaging them on these pages https://www.facebook.com/turbotax/ and https://twitter.com/TeamTurboTax
You bought the Windows Desktop program? Then you need to call in and ask for the Mac program.
Contact Customer Service (You need to pick the CD/Download program in the product drop down box.)
What is the Turbo Tax phone number