Prior year tax returns can only be printed and mailed, they cannot be e-filed. Print, sign, date and mail the tax return to the IRS. Include with the mailed return any forms W-2 and 1099 which have taxes withheld. There are no penalties for filing a tax return after the due date if filing for a tax refund or there are no taxes owed.
When mailing multiple tax years use a separate envelope for each tax year. Consider using a tracking serviced, return receipt required, from the US Post Office so that you will know that the mailed tax returns were received.