Use Tool 'DxO Smart LIghting'. In top panel choose Uniform, then in Mode drop-down menu 'DxO OpticsPro 7'. You will then see sliders for Black and White Points.
Unfortunately in DxO 12=PhotoLab, these mode options have been dropped and edits made using them no longer carry through. If you value this adjustment, keep a copy of DxO 11 when you upgrade.