For 2019?  Sorry, Online for 2019 and prior is closed now so you can not start a new 2019 or 2018 return or finish one. Online is only for 2020. Oct 15, was the last day to efile.  2019 is now the prior year. If you entered 2019 into the 2020 online version you should clear out your online return so you can use it for 2020.
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-onli...

If you went to the end and actually submitted a return you need to wait until the IRS opens Jan 27 or later and see if it is Accepted or Rejected. If it is Rejected you can change it around to be for 2020. But if they Accept it you have a problem and will need to amend.

Did you start an Online return? How to finish a prior year online return
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...

Or How to file a prior year
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-prepare-a-prior-year-tax-return/00/25...

You can only buy the download for prior years. You have to buy a separate program for each year. They only sell the last 3 years. You need a full Windows or Mac computer to install it on. Buy the download here
https://turbotax.intuit.com/personal-taxes/past-years-products/

You have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.

Important! Mail Federal and State in separate envelopes and mail each year in separate envelopes.

If you are getting a refund, there is not a penalty for filing past the deadline. You have 3 years to file for a refund. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.

If you want to file for free you can fill out the forms by hand. Here are some basic forms…..

Here is the IRS 2019 Form 1040
https://www.irs.gov/pub/irs-prior/f1040--2019.pdf

or if you want bigger type use 1040SR for Seniors,
https://www.irs.gov/pub/irs-prior/f1040s--2019.pdf

And 2019 Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2019.pdf

2019 Tax and EIC Tables
https://www.irs.gov/pub/irs-prior/i1040tt--2019.pdf

Sch 1 : https://www.irs.gov/pub/irs-prior/f1040s1--2019.pdf
Sch 2 : https://www.irs.gov/pub/irs-prior/f1040s2--2019.pdf
Sch 3 : https://www.irs.gov/pub/irs-prior/f1040s3--2019.pdf
Then when you do file 2020 enter 0 for the 2019 AGI since you are filing 2019 late.

Online tax preparation and e-filing for 2019 returns is now permanently closed.  You had until midnight on Thursday, October 15, 2020 to finish and attempt to e-file; if your e-file was rejected you had until October 31, 2020 to make corrections and re-file. Now it is too late to use online software or to e-file. If you have any changes/corrections at all to make to your 2019 return, you now have to complete it using desktop software, which you must download to a full PC or Mac  (not to a mobile device).Then you need to print, sign and mail it.

https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...

If you already paid for your online software you can ask customer support for a download of the desktop software.

They are available from 5 a.m. to 5 p.m. Pacific time Monday-Friday.

https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number

If you are getting a refund, there is no penalty for filing late.  If you owe tax due, then file and pay the amount due as shown on the Form 1040, but expect a bill later from the IRS for the penalty and interest you will owe.  Only the IRS will calculate this—TurboTax will not calculate it.