Hi Linda and welcome to our community
Look at your toolbars. Near the 100% field you should see an
icon that looks like a notepad with a pen. Clicking this icon will
allow configuring a different style sheet. Or, you could also look
at the topic properties. Click the Appearance tab. As this is a
Windows application, RoboHelp HTML follows suit and allows about
four or five ways to accomplish any task.
Associating more than a single sheet to a topic isn't really
possible. At least not directly. I'm thinking you would have to
script something.
Cheerx... Rick