If it has been rejected then you can simply make the corrections required to fix the rejection AND at the same time add the new information, and re-submit your CORRECTED e-filed return.
If it has been accepted you will have to prepare and mail an amended return ---BUT WAIT until you receive your refund before filing the amended return.
A Form 1040-X amended return MUST be PRINTED and MAILED; and usually takes 3-4 months to be processed. Form 1040-X is usually not available until mid-February.
Perhaps some terminology/definitions would be in order:
AMEND:- your return is what you do AFTER your return has been filed and accepted by the IRS and/or state. (No additional charge)
CHANGE:- your return is what you do BEFORE your return has been filed --simply go back to the respective information and change it as needed.
CORRECT:- your return is what you do AFTER you attempted to file your return and it is rejected by either IRS, or state --again, simply go back to the respective information and change it as needed.
Above all DO NOT DO ANYTHING until you find out if your return is rejected or accepted.
NOTE: When mailing a printed return it is always a good idea to go to the Post Office and mail it 'Certified' with 'Return Receipt'. That way you will have proof that they received it and when it was received
Fixed the mistake but still can't file again it says it's waiting on other forms? Very confused by this?
Once you selected that you can be claimed by someone else that probably triggered a form that is not ready for e-filing in TurboTax. In this case it is probably form 8615. According to the information here that form will be ready by 3/5/2020.