The TurboTax online editions are Only for tax year 2018.
Clear all the 2017 tax data you entered on the 2018 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 with a lower priced edition. Click on Tax Tools on the left side of the program screen while working on the 2018 online tax return. Click on Clear & Start Over.
If you choose to use TurboTax to complete and file a 2017 tax return 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.