The TurboTax online editions are only for tax year 2018.
To access your prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created. TurboTax does not store online any returns completed using the desktop editions.
You can also 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
See this TurboTax support FAQ for when access to prior year online tax returns expire - https://ttlc.intuit.com/community/prior-year-return/help/when-does-access-to-my-prior-year-turbotax-...
In TurboTax Free Edition, you can purchase PLUS to unlock your prior-year .tax file.
The exact instructions will vary depending on the status of your 2018 TurboTax Online return (select one):
