The Add CSS Rules Pane
The Add CSS Rules pane allows you to add new rules to the currently selected element or element type (this element or type is selected with the Choose Parent and Choose Target Child menus).
Set a rule by choosing the rule from a drop down menu
and entering the value for that rule in the form field below
Define up to three rules this way then click the "Add Rules" button.
Note that the drop down menu will only be populated with rule names that are not already set for this element. If you've specified a value for 'Padding', for example, 'Padding' will not appear in the menu as an option for adding new rules (as is the case in the above graphic).