It depends on whether your are e-filing your return, or printing it for mailing.
If you're e-filing, you sign your return in Step 1 under Finish & File. Signing for electronic filing means providing your 2022 Adjusted Gross Income (AGI) and entering a five-digit PIN that you make up yourself.
If you are printing and mailing in your return, signing means using a pen to sign the bottom of page two of Form 1040 in the section called Sign Here.