Do NOT change anything on the return that has been filed. TurboTax will send you an email when the IRS either accepts or rejects the tax return.
If the IRS rejects the return you can add the W-2 and re-file. If the IRS accepts the return, then you must wait for the tax refund or the taxes owed and paid to be processed. You would then have to file an amended tax return, Form 1040X, to add the W-2 to the accepted tax return. An amended federal tax return can only be printed and mailed, it cannot be e-filed. The IRS will take 16 weeks or longer to process the amended tax return.
See this TurboTax support FAQ on amending a 2016 tax return - https://ttlc.intuit.com/questions/3061514-how-do-i-amend-change-or-correct-a-2016-return-with-turbot....
Nothing at this time.
Already E-Filed and Need To Change
If you have already E-filed your tax return and need to make a change for any reason, then you have no choice but to wait until the IRS processes your E-filed return. If the IRS rejects your E-filed return, then you can just make the necessary changes and resubmit it.
If the IRS accepts your E-filed return, then you must WAIT until the IRS has processed your return. If you have a refund due your return is not processed until you have received your refund. If you owe taxes, your refund is not processed until you have paid those taxes and your payment has cleared your financial institution. Once processing is complete, you will need to file an amended return. You can not e-file an amended return. The IRS says you can’t. You have to print it, sign it (both the 1040 and 1040X) and physically mail it to the IRS.
If your E-Filed return is pending, and you change anything on your copy of your return, then you are guaranteed to have major issues with correcting or amending it later. So for your own sanity, do not touch anything until it’s time, as clarified above.
An amended return must be printed, signed and mailed. The IRS says so.