I forgot to file my Form 8962 Premium Tax Credit and I've already submitted my return. Can I edit this?

[DaraLO]

Once you've filed your tax return, do not make any changes until the IRS either accepts or rejects your return.

If accepted, wait until the IRS issues your refund (if applicable), then you will need to amend your return.  The following TurboTax FAQ can guide you when you are ready to amend:  How do I amend my 2019 TurboTax Online return? - Community

If rejected, you can sign into your TurboTax Online account and fix what caused the rejection.  At this time, you can also add your Form 8962 information.  Refer to the following FAQ for assistance:  How do I fix a rejected return? - Community