First make sure that you really need to amend and your 2015 tax return was accepted (or paper filed) in your TurboTax timeline.
 1.Then sign in with the log in you used for your 2015 tax return.
 2.Click or tap on 2015 tax year in your tax timeline (you may need to first click or tap "load my tax timeline" in the right corner.
 3.In the some things you can do section click or tap amend (change) 2015 return.
 4.Follow the onscreen instructions in the how to amend your 2015 return pop-up window.