You cannot use the TurboTax online editions for tax year 2019 to enter a 2016 W-2. Clear the tax return and start over for 2019. The 2016 W-2 can only be entered on a 2016 tax return.
If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return and start over. Click on Tax Tools on the left side of the program screen while working on the 2019 online tax return. Click on Clear & Start Over.
To complete and file a 2016 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2016 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/2016
