Yikes! You now have to Amend that return to be for 2019. You have to delete the 2018 info and enter 2019.
How to amend an Online return
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/
Amended returns can only be MAILED not efiled.
Then if you still need to do 2018. To do 2018 you have to buy the Desktop Download program here
https://turbotax.intuit.com/personal-taxes/past-years-products/
Or If you have a simple return You can fill out the blank forms for free.
Here is the IRS 2018 Form 1040
https://www.irs.gov/pub/irs-prior/f1040--2018.pdf
And instructions https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf
2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf
IRS 2018 Schedules 1 thru 6 (only if needed)
https://www.irs.gov/pub/irs-prior/f1040s1--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s2--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s3--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s4--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s5--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s6--2018.pdf
