Your prior message for the same subject already answered here - https://ttlc.intuit.com/community/taxes/discussion/i-did-not-finish-filling-my-2018-taxes-due-to-browser-issues-will-i-still-get-charged-on-my-credit/01/915828
You cannot use the 2019 program to file your 2018 tax return. In order to file your 2018 tax return, you would need to purchase the download version of TurboTax for 2018 and then print and mail your return. Your 2018 return cannot be e-filed at this point.
One of the biggest reasons you cannot use different year software is because laws and forms change from year to year.
I need to know how I can finish filling my 2018 taxes
If you started your 2018 taxes in TurboTax, here are the instructions to finish: How to complete a prior year return started in TurboTax.