There is no way to "unsubmit" your tax return if you already submitted it. Submitting it is like putting a paper tax return into a mailbox. It's on it's way and there's no way to get it back.
You will have to first wait to see if your tax return is accepted or rejected. That probably won't happen until after February 12. If it's rejected you can add the missing W-2 when you correct the reason for the rejection, and resubmit it.
If your tax return is accepted, you will have to then wait until the IRS finishes processing it and you get your refund. Then you will have to file an amended return, Form 1040-X, to add the missing W-2. Here is a link to the instructions for filing an amended return.
How do I amend my 2020 TurboTax Online return?
