Can I add a dependant on 2023 fed and state tasxes

Are you just now preparing your 2023 return?   Are you using the desktop software for 2023---you cannot use online for a 2023 return.  Dependents are entered in MY INFO.

Or....are you trying to amend a 2023 return that you already filed?

Wait until your original return has been fully processed before you amend, and make sure you have saved a pdf of the original return before you amend.

See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...

Do not expect quick results from amending. It can take four months or more for the IRS to process an amended return.  

You can watch for information here:

https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1