You will have to amend the 2017 tax return that was filed to add the 2017 W-2.
See this TurboTax support FAQ for amending a 2017 tax return originally completed and filed using TurboTax - https://ttlc.intuit.com/questions/4252298-how-do-i-amend-a-2017-return-in-turbotax
If you did not file a 2017 tax return then you will need to purchase, download and install on a personal computer one of the 2017 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2017 tax return can only be printed and mailed, it cannot be e-filed.
