You will go in and Amend the 2018 State return after your return is fully processed and the
Amended return process for TurboTax is up and running.
Only difference with your Amended return is it will State of Ohio only and not the Federal return.
Once the return has been filed it cannot be stopped (unless you get extremely lucky and IRS would reject it for some reason).
So you have to wait for the return to be processed and you get your refund.
Then approx February 28th you can sign back into TurboTax and do the Amended return.