I read this article in the forums which deals with the same issue.
Unfortunately, I didn't see any get_sidebar code in page.php and function.php so the solutions offered in the forum aren't applicable in my site. I also saw a sidebar.php in my theme's templates, and I think the theme I'm using is using a different code?
Simply, I want to remove the sidebars in my forums page. And if anyone could tell me how to widen the container of that page, I would appreciate it, too. I will post the codes for in my site.