TurboTax does not support tax years 2018 or 2019.
You will need to find a local tax professional to assist you in completing those prior year tax returns.
Note - Any tax refund on the 2018 or 2019 tax return will not be paid as it is beyond the three year timeframe to file from the due date of the tax return.
TurboTax software is only available for tax years 2020, 2021, 2022 and 2023. TT no longer provides nor supports software for 2018 or 2019. Any refund for 2018 or 2019 has already been forfeited; it is too late. However, if you owe tax due for 2018 or 2019, you still have to pay the IRS with late penalties and interest.
You can seek local paid tax help, or we can provide links to the paper forms that you can prepare by hand to mail in.
2018
Instructions for Form 1040 (HTML)
https://www.irs.gov/pub/irs-pdf/f1040s1.pdf
https://www.irs.gov/pub/irs-pdf/f1040s2.
https://www.irs.gov/pub/irs-pdf/f1040s3.pdf
https://www.irs.gov/pub/irs-pdf/f1040s4.pdf
https://www.irs.gov/pub/irs-pdf/f1040s5.pdf
https://www.irs.gov/pub/irs-pdf/f1040s6.pdf
2019
2019 Instructions
https://www.irs.gov/pub/irs-prior/i1040gi--2019.pdf
1040 https://www.irs.gov/pub/irs-prior/f1040--2019.pdf
1040SR https://www.irs.gov/pub/irs-prior/f1040s--2019.pdf
2019 Schedules 1-3
https://www.irs.gov/pub/irs-prior/f1040s1--2019.pdf
https://www.irs.gov/pub/irs-prior/f1040s2--2019.pdf
https://www.irs.gov/pub/irs-prior/f1040s3--2019.pdf