Unfortunately, if you have already e-filed your return, you would not be able to add another W-2. You would need to wait until your return is either accepted or rejected. If it's rejected, you can simply go in and fix the error, add the W-2 and re-submit your return. If it's accepted, you would want to wait until you receive your refund and then use the link provided below to amend your return:
How do I amend my 2020 TurboTax Online return?
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