I was told by a Verizon employee (who admittedly might not have had a clue as to what he was talking about) that it doesn't have that function. I came from the S5 which had that and I loved it, so if the S6/S6 Edge does have this function I would love to know how to enable it (as I have been unsuccessful in locating it in the settings menu anywhere myself).
I'm guessing they did away with it for the S6. I contacted Samsung via live chat and asked, and the representative gave me incorrect information (said it was under Settings>>Sound & Display>>One handed operation, but there isn't even a Sound & Display option. It's Display and wallpaper and Sound and notifications).
I did find one on the Samsung Galaxy S6. Go to settings, Advanced Features, and at the top it will say "One-handed operation". Touch that, and you will get two things to toggle, the first of which is "Reduce screen size", and the second one says, "One-handed input". Hope that solves the issue.