If they filed a 2015 tax return then they need to amend the 2015 return that was filed to add the tax data from the 2015 W-2's to the original tax return using IRS Form 1040X. An amended tax return can only be printed and mailed.
If they did not file a 2015 tax return, then they can file one now. A 2015 return can only be printed and mailed.
Go to this IRS website for free forms, schedules and instructions - https://www.irs.gov/forms-pubs
