I received an extension to file for 2016. I need to edit the amount of federal estimated taxes paid, but it won't let me. What do I do?

I actually forgot to enter a 1040ES that I paid, but TurboTax doesn't seem to let me add that in now.  It simply tells me, "You paid a total of ___ in federal estimated taxes," but doesn't give me the option to update or change it.