If you have just filed your returns, you need to wait to amend them until the original Federal return has been processed by the IRS (refund issued / payment processed). Wait until the State return has been processed by your State tax agency before amending the State return.
Once you have confirmed that the Federal return has been processed, if you used TurboTax Online, log in to your account and select “Amend a return that was filed and accepted.”
See here for more information on preparing an amended return with TurboTax.