Estimated taxes are entered under Deductions & Credits > Estimates and Other Taxes Paid. 

To enter your 2016 estimated state taxes in TurboTax:

• Continue your return in TurboTax Online. (If your return isn't open, you'll need to sign in and click Take me to my return.)
• Click My Account (top right of your screen).
• Select Tools.
• In the pop-up window, select Topic Search.
• In the search bar, type estimated.
• In the results box, highlight estimated tax payments, then click GO.
• You'll land on the Estimates and Other Income Taxes page. Click Start next to the State estimated taxes for 2016. (Click the first screenshot below for reference.)
•  Follow the onscreen instructions to enter your quarterly state estimated tax payments. (Click the second screenshot below for reference.) 

Note: If using the TurboTax CD/Download software, you'll use the Find function (instead of "My Account") to search for the topic.

[Edited 04/17/2017]