You will either have to file a 2021 tax return if you have not already filed and complete the Recovery Rebate Credit section. Or you will have to amend the 2021 tax return that has already been filed.
Check your IRS tax account to verify that the IRS has not already sent you the $1,400 stimulus payment for 2021 - https://www.irs.gov/payments/online-account-for-individuals
See this TurboTax support FAQ for amending a prior year tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...
To complete and file a 2021 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2021 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2021 tax return can only be printed and mailed, it cannot be e-filed using TurboTax.