How do I file for 2020 and 2021?

Each tax year is separate.   Do not try to combine them in ANY way.

The current online program can only be used for a 2021 return--no other year.  And if you did not file a 2020 return you will have trouble e-filing 2021.  When it asks for your 2020 AGI try using zero.  If zero does not work then you have to print, sign and mail 2021.

Online preparation and e-filing for 2018 and 2019 and 2020 is permanently closed.

To file a return for a prior tax year

 If you need to prepare a return for 2018, 2019 or 2020 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 UPS or 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.

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.