If your return has already been accepted by the IRS, then you will need to file an amended return to add your additional W-2.
If your return is rejected for any reason, then you can include the W-2 before you resubmit it.
You should wait until your return has been fully processed and your refund has been received if you are expecting one before amending. Also, be sure that you have received all expected income documents so that you will only need to amend one time. Then, use the instructions in the following TurboTax article to amend your return:
How do I amend my 2019 TurboTax Online return?
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