You cannot e-file a 2017 tax return. Go back and change your filing method to Mail
That doesn't matter and is not needed. You can only print and mail prior year returns. Just ignore the error message. Sign your return in ink and date it the day you sign it.
You have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.
Where to mail federal paper returns
https://www.irs.gov/uac/where-to-file-paper-tax-returns-with-or-without-a-payment