I need to complete returns for 2019 amd 2020. How do I download them?Thank you

Sorry---software for 2019 and 2020 is no longer available and is not supported with updates or downloads for state software.   And it is too late to receive refunds for those years--any refund shown on a 2019 or 2020 tax return has been forfeited and will not be paid.   If you owe tax due you still owe it, though, with interest and late filing penalties.   

You might want to seek local paid help for those years.

Are you also behind for 2021, 2022 and 2023?

Each tax year has to be filed separately using the forms for the specific tax year.  They cannot be combined in any way--do not even put them in the same envelope when you mail them.  Software for past years is available back to 2021.  Any earlier years can only be prepared on paper forms by hand--and those refunds have been forfeited now.

The current online program can only be used for a 2024 return--no other year.  And if you did not file a timely 2023 return you will have trouble e-filing 2024.  When it asks for your 2023 AGI try using zero.  If zero does not work then you have to print, sign and mail 2024.

You cannot change the tax year.   The current online program is for 2024 only.   Only a 2024 return can be prepared online and only a 2024 return can be e-filed.

Online preparation and e-filing for 2021, 2022, and  2023 is permanently closed.

Note:  The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac.  It cannot be used on a mobile device.

To file a return for a prior tax year

 If you need to prepare a return for 2021, 2022, or 2023  you can purchase and download desktop software to do it, then print, sign,  and mail the return(s)

https://turbotax.intuit.com/personal-taxes/past-years-products/

You may also want to explore purchasing the software from various retailers such as Amazon, Costco, Best Buy, Walmart, Sam’s, etc.

Remember to prepare your state return as well—if you live in a state that has a state income tax.

https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/00/25573 

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 certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

You might have difficulty finding those programs. A professional tax preparer might help or you can download the forms from the IRS website if you have a simple return. You can’t get a refund from retuns that old. 

Some other tax software companies might still have software for 2019 and 2020 available.