You should not amend a return until both your federal and state have been accepted and you have received the refund (if you are getting one) from both. Do not change your original return until you begin the amended return form 1040X. The amended return must be printed, signed, and mailed. It can't be efiled.
Here are instructions for how to amend: https://ttlc.intuit.com/questions/4667233-how-do-i-amend-a-2018-return-in-turbotax
