Each fixture has variables and options for maximum control. By selecting a fixture in the outliner or patch view, you can make changes to any fixture in Unreal Engines "Details Panel". If this is not already visible to you, you can enable the view by clicking Window - Details.
Once you have a fixture selected, you will see many sections that allow for manual control over Carbon assets.
Note: Multiple fixtures can be selected by holding either 'Ctrl' or 'Shift' on your keyboard. However, fixtures can only be modified per Fixture Type.