After you file


@Katewagerman wrote:

Ok so wait until the refund is issued and then mail in that form with the W2?


After you receive your refund, you need to open Turbotax back up and prepare an amended return.  You adjust your own tax return by adding the missing W-2.  You might get another refund or you might owe tax.  The amended return includes a complete new copy of your corrected tax return plus a cover sheet summarizing the changes.  You will probably be able to e-file your amended return through Turbotax.

 

At this point, Turbotax can't prepare amended returns and there aren't even instructions yet.  That function will probably be added to the program in March or April.  Right now, they are prioritizing implementing all the IRS changes for this season.