How do I file for recovery rebate credit

TurboTax does not know who will receive the stimulus checks that the IRS is sending.   The IRS has identified some people who were eligible for the 3rd EIP payment who did not receive it and did not use the recovery rebate credit on their 2021 tax returns, so the IRS is sending out those payments.   You should check your online account with the IRS---many people received the 3rd stimulus before they filed their 2021 return, so they did not need to use the credit on their tax return.

Look at your online account with the IRS to see if they sent you $1400 in 2021.

https://www.irs.gov/payments/your-online-account

If you could be claimed as someone else's dependent in 2021, you are not eligible for the payment.

If you were eligible and do not receive a payment soon from the IRS, the other way to get the payment is to amend your 2021 return to use the recovery rebate credit before April 15, 2025.   If you did not file a 2021 return at all, then prepare one and mail it in.

2021

https://www.irs.gov/pub/irs-pdf/i1040gi.pdf

Here is the IRS 2021 Form 1040
https://www.irs.gov/pub/irs-prior/f1040--2021.pdf

or if you want bigger type use 1040SR for Seniors,
https://www.irs.gov/pub/irs-prior/f1040s--2021.pdf

And 2021 Instructions
https://www.irs.gov/pub/irs-prior/i1040gi--2021.pdf

2021 Tax and EIC Tables
https://www.irs.gov/pub/irs-prior/i1040tt--2021.pdf

Sch 1 : https://www.irs.gov/pub/irs-prior/f1040s1--2021.pdf
Sch 2 : https://www.irs.gov/pub/irs-prior/f1040s2--2021.pdf
Sch 3 : https://www.irs.gov/pub/irs-prior/f1040s3--2021.pdf