Making it look “nice” will depend on what you personally want/need. You would have to either create your own custom design using css or you could use a bbpress template.
If you’re having issues setting up the forum index, and other things, then you would definitely need to visit their forums since the theme itself doesn’t affect the functionality of the plugin and how it works.
Also, do a search for some of the plugins that integrate Genesis with bbpress. Here’s one – http://wordpress.org/plugins/bbpress-genesis-extend/ I think there might be more, but I can’t remember what they’re called.
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