If you have already
filed your tax return, then your only option will be to wait and see if your
return is accepted by the IRS.
If the return ends up being rejected by
the IRS, then you will have an opportunity to make the corrections (add second W-2) you
want to your tax return and resubmit it.
If your return is accepted by the IRS, then
you must file an amended return (Form 1040X) to add the additional W-2. Below is a link
with more information on filing an amended return. And note that amended
returns must be mailed as they cannot be e-filed.
https://ttlc.intuit.com/replies/3288565
