To use TurboTax for the 2015 and 2016 tax returns you will need to purchase, download and install on a personal computer one of the desktop editions for each tax year from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
Prior year tax returns can only be printed and mailed, they cannot be e-filed. Use separate envelopes when mailing multiple tax years.