Did you already e-file? If you already e-filed, you will have to wait for the original return to be fully processed and then amend to add that W-2.
If you have not yet e-filed:
Go to Federal>Wages & Income to enter a W-2.
After you enter the first one, you click Add Another W-2.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**