You will have to do an amendment to enter the
information from that W-2. It cannot be
entered in your 2016 return. Please
see the one page article from the IRS on Tips For
Filing An Amended Return, this article should help to guide you as to, whether or
not you should file an amendment based on the changes on the W-2. Not all
changes would require an amendment.
If you do have to file an amendment, please
see the link below to get the process started. However, don't worry,
you generally have 3 years to amend your taxes, unless you will owe, then it
would be best to do it as soon as possible after receiving your refund, to
avoid penalties and interest. I would recommend that you wait until after receiving your refund before working on
your amendment as this could delay the process.
https://ttlc.intuit.com/replies/3288565