I did my 2016 Federal return online with TurboTax in March 2017 to get a handle on my quarterly obligations for 2017. How do I find my 2016 return information?

https://ttlc.intuit.com/questions/3402465-how-do-i-access-my-prior-year-2016-or-earlier-return

You can get a free transcript from the IRS:   

https://www.irs.gov/individuals/get-transcript

How do I get a copy of a return I filed using online TurboTax?

https://ttlc.intuit.com/questions/1900748

How do I get a copy of a return I prepared using desktop TurboTax?

https://ttlc.intuit.com/questions/1900639