Creating a new style using the Style dialog
To create a new style using the Style dialog, right-click in the Styles and Formatting window and select New from the pop-up menu.
(Cell styles only) If you want your new style to be linked with an existing style, first select that style and then right-click and select New.
If you link styles, then when you change the base style (for example, by changing the font from Times to Helvetica), all the linked styles will change as well. Sometimes this is exactly what you want; other times you do not want the changes to apply to all the linked styles. It pays to plan ahead.
The dialogs and choices are the same for defining new styles and for modifying existing styles.