The only way to use TurboTax for the 2017 amended tax return would be to exactly recreate the 2017 federal tax return that was originally filed. Then print the tax return so the software assumes that the 2017 return was filed. After that you could amend the 2017 tax return. You would have to use one of the 2017 desktop editions installed on a personal computer to start this procedure. The lowest cost 2017 desktop edition edition is the Deluxe edition at $79.99 - https://turbotax.intuit.com/personal-taxes/past-years-products/
The IRS has a copy of your 2017 amended tax return.
You can get free transcripts of your federal return from the IRS - http://www.irs.gov/Individuals/Get-Transcript
For a fee of $50 you can get a complete federal tax return from the IRS by completing Form 4506 - http://www.irs.gov/pub/irs-pdf/f4506.pdf