[fel64]

You have to do it differently. To apply a css file, make a new folder in /bbpress/ called my-templates, open it, make a new folder for your “theme”, and put in your css file called style.css. Now go to the Admin Panel > Presentation and pick your theme.

Note that you can change the HTML output of files as well. If you do not have a file for a particular page (such as forum.php) bbpress will look for the default file (located in /bbpress/bb-templates/kakumei) and use that instead. If you wish to use a modified file, copy the default into your theme’s folder and change it there.