It is too late to get the stimulus payments from 2020. The deadline for that was May 17, 2024. If you filed a 2021 return and did not use the recovery rebate credit and did not already receive the 2021 stimulus payment, you may need to amend your 2021 return to get the credit. Or if you did not file 2021 at all, you can file a 2021 return to seek the credit if you do so by April 15, 2025. After 4-15-2025 it will be too late.
There is nowhere on a 2024 return to enter anything about stimulus checks. The only way to seek the 2021 stimulus money is on a 2021 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