To add your own styles to the styles drop down list in the PowerCMS:
1. Reenter the HTMLEditor in Dreamweaver (from the Properties Window)
2. On the Quick Insert Click the Customize Button
3. On the Edit Settings click the Styling Tab
4. Click the Folder Icon to browse to your style.css file
5. a list of the classes in the file should be listed
6. select the classes that you want to show in the styles drop down list
7. Click OK, and OK
Let me know if you have any questions about these steps.