Hi, I'd like to know where I add my 2021 tax return?

You are being asked for your 2021 AGI, so that you can e-file 2022.   The question for AGI appears in the FILE section.

Where do I find my AGI?

https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/27010/message-id/746

Your 2021 tax return shows your 2021 Adjusted Gross Income  (AGI)  If you filed a joint return then the AGI is the same for each of you.

Form 1040        line 11

If you are using the same TT account that you used last year, you should also be able to find this number in your Tax Home for 2021

If entering the amount from your 2021tax return does not work, then try entering “0” instead.  If that does not work and you still cannot e-file, then print, sign, and mail your tax return.

You can get a free transcript of your past return from the IRS:  

https://www.irs.gov/individuals/get-transcript

Note: If you filed late or amended your return, your correct 2021 AGI may not be in the system. 

https://ttlc.intuit.com/questions/1944348-how-do-i-print-and-mail-my-return-in-turbotax-online

Note:  If you mail your federal return, you will also need to mail your state return.  You will not be able to e-file your state return.

https://ttlc.intuit.com/questions/3415597-what-if-i-entered-the-correct-agi-and-i-m-still-getting-an-e-file-rejec

https://ttlc.intuit.com/questions/1944348-how-do-i-print-and-mail-my-return-in-turbotax-online

it is a good idea to use a mailing service that will track it like UPS or certified mail.  Then you will know the IRS received it.

If you used the wrong AGI, your e-file  be rejected.  When you get the rejection notice, correct it and re-file.

https://ttlc.intuit.com/community/agi/help/where-do-i-correct-my-agi-in-turbotax-online/00/26311