Yes.  Are you having a problem filing it?

how do I mail in a return

Did you print it out?  It should say on the instruction page or look it up here……
<a rel="nofollow" target="_blank" href="https://www.irs.gov/uac/where-to-file-paper-tax-returns-with-or-without-a-payment">https://www.irs.g...>

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.

Is not late for send 2016?

No, still not too late.  Basically, you have three years to do it.

You have to print and mail prior year returns. Do you need to prepare a 2016 return?

Where can I find my 2016 return to finish and submit ?

Did you start it in the online version?  How to finish a prior year online return     <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...>