If you asked the plan trustee to withhold taxes for you, that should be recorded on the 1099-R form in box 4 (federal) and box 12 (state). Turbotax will automatically include those withholding amounts in its calculations when you enter the 1099-R.
If the withheld taxes are not recorded on the 1099-R, you need to get a corrected 1099-R from the plan trustee.
