You can create a new style sheet at the same time that you create a new topic.
Click New
Topic .
In Topic Title, enter the title of the topic. The Create Topic Wizard opens.
Click the Appearance tab.
Click New.
In File name, enter a name for the style sheet. The file is saved using the .CSS extension (for Cascading Style Sheet).
Click Save. 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.
Click OK to close the Create Topic Wizard.
The new topic is created. It is linked to the new style sheet and displays the style formats in the WYSIWYG Editor.
Tip: You can link this style sheet to other topics in your Help project. For details, see Linking style sheets to topics.
Note: When you create an external style sheet, it will include all default styles.