From the Format menu, select Styles.
Click New Sheet. The Create New Sheet dialog displays.
In Name, enter a name for the style sheet. The file is saved using the .CSS extension (for Cascading Style Sheet).
In Folder, select a location for the new style sheet from the drop-down list.
If you want to base your new style sheet on an existing one, select the check box next to Copy styles from and select a style sheet from the drop-down list.
Click Create. The Styles dialog opens. Use this dialog to create new styles for the style sheet.
When you finish, click OK. The new styles are saved in the new style sheet.
Tip: You can link this style sheet to other topics in your Help project. For details, see Linking style sheets to topics.