1099B Box 4 (Federal Tax Withheld). I entered them by section (long term, short term, etc) and can't find any way to input Box 4. How do I do that?

Enter the withholding in the Estimates Paid section.   Go to Deductions and Credits, then scroll down to Estimates and Other Taxes Paid.

Click Start next to Other Income Taxes, then scroll down to Other Income Taxes Paid in 2023 > Withholding not already entered on a w-2 or 1099.  Answer Yes, and then enter the amount in the Federal Withholding box.