Full Width, No Side Bar Choice

Using Adventurous I am trying to make pages have no side bar and full width. I can set this for individual pages but struggling with ones produced by the bbPress plugin which seems to use another page template and I cannot change it within the theme. bbPress say I should take the template page for "no side bar, full width", copy it and rename it bbpress.php but I am struggling to work out which file it is. Can you help?