If you need to amend a 2016 tax return completed with the online editions and your computer is a Mac then you will need to contact TurboTax support so they can push a 2016 desktop Mac installation file to your download account.
Use this website to contact TurboTax support - 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
