QCDs are only permitted to be made from IRAs and only after you have reached age 70½.
Do not use overrides. Enter the Form 1099-R exactly as received under Wages & Income-> Retirement Plans and Social Security -> IRA, 401(k), Pension Plan Withdrawals (1099-R). Make sure that the IRA/SEP/SIMPLE box is marked on TurboTax's 1099-R form as it should be on the Form 1099-R provided by the payer. In the follow-up, when asked, indicate that you had the IRA custodian transfer some or all of the distribution to charity and indicate the amount. TurboTax will automatically include the gross amount of the distribution on Form 1040 line 15a or Form 1040A line 11a but exclude the QCD amount from the amount on line 15b or 11b. TurboTax will also put the notation "QCD" next to the line.
