Since you have already filed the return, you must wait until the IRS either accepts or rejects the original tax return before you can amend.
Once your original return has been accepted (and you have received your refund) or rejected, you can then add the new W-2 to your tax return.
Please see these instructions for amending a return in TurboTax Online:
https://ttlc.intuit.com/replies/5567856
Once the return is available for editing, use the instructions below to add the W-2:
- On the Tax Timeline menu at the
top of the screen, select "Federal Taxes".
- Select "Wages and
Income" underneath on the second menu bar.
- Select "Edit/Add"
next "Job (W-2)" to view a summary of all W-2's entered
on the return.
- On this screen, select the
"+Add another W-2" button to add income.
