There's no way to do it in Fireworks alone. You need to apply CSS styling to the text in Dreamweaver. Something like this:
Oh ! Ok, I spent so much time looking thinking fireworks would have such a basic functionality ... Now I am wondering if this firewors tool is really up to date as it uses table instead of Div ?
Fireworks is not a WYSIWYG editor. It's a tool for creating web graphics rather than entire web pages. You can use it very effectively for website mock-ups too.