The pencil icon wont be in the web page that you view in the browser. the pencil icon will be in the HTML Eidtor dialog box.
open the page in Dreamweaver, select the HTML Editor instance on the page and click the edit button in the property inspector.
click the edit icon next to the preset name.
then go to the styles tab.
you can select the style sheet to use, the you can edit the styles that will be listed in the styles drop down.