After you file

if your parents can claim you, you are not entitled to the stimulus payment.

 

That aside, if you amend for the stimulus payment your 1040-X should show a refund of at least $1,800 immediately.

 

1040-X becomes your new 2020 tax return and that's how you get the EIP payments

 

You may need someone to help you with form 1040-X.