How can I file a previous year tax return?

[mesquitebean]

Did you already start a prior-year online return that you need to download and finish?  Or do you need to start from scratch?

Either way you'll need to purchase the desktop software (CD/download) for that year.  If you already paid online, TurboTax Customer Support can furnish you a download.

Otherwise, here's where you can purchase the prior-year software directly from TurboTax.  You may also find it at a reputable authorized retailer such as Amazon.

https://turbotax.intuit.com/personal-taxes/past-years-products/ 

A past-year return cannot be efiled.  It has to be printed, signed, and mailed.