Get your taxes done using TurboTax

If you have not already e-filed, you can go back and add the additional income under wages and income tab. 

To add another W-2 please follow the steps below:

  1. Open (continue) your return in TurboTax if you don't already have it open.
  2. Inside TurboTax, search for W-2 in the search box in the upper right-hand of the TurboTax screen (upper- or lower-case, with or without the dash) and then select the Jump to W-2 link in the search results.
  3. Proceed to the Here's your W-2 info and select add another W-2

Unfortunately, if you have already e-filed your return it is too late. Once you transmit your return you cannot change it or get it back. You would have to wait until your return gets rejected or accepted.  If rejected, you can make your changes or add information to your return. If accepted, you would need to amend your return to correct or add information to your return. 

If you need to amend your return and you're amending to claim more money, the IRS says to wait until you've received your original refund before filing an amendment. Once you've received your original refund, feel free to cash or spend it while your amendment gets processed (this can take 12–16 weeks). 3 weeks after you mailed your amendment, you can start tracking its progress at the IRS Where's My Amended Return? site.

More information regarding amending a return can be found below: 

https://ttlc.intuit.com/replies/3288565