You'll enter it on the 1099-R screen by clicking Federal Taxes, then Wages & Income, then scroll down to Retirement Plans and Social Security, then IRA, 401(k), Pension Plan Withdrawals (1099-R), and follow the prompts.
You'll come to the screen where TurboTax asks you to enter the 1099-R information, and you'll notice toward the bottom are boxes 12-14. This is where you'll enter the state information from the 1099-R, and box 12 specifically is for "State Tax Withheld."
