GWT -> Configuration -> URL Parameter. On my site, Google found it them self, it is set as page and let Googlebot decide. I think if you set it to no, Google treat
http://xenforo.com/community/resources/?page=2 as the same as
http://xenforo.com/community/resources/, yes, it will treat them as individual pages. While you don't provide the exact duplicate content error you receive, my guess is that you get duplicate title tags. To solve that, you might have to slap on a | Page 2 in the title tag, as the forum posts does.
EDIT: To clarify, I do not use Resource Manager, same parameter is probably in use elsewhere on the site, or it is in the default package without friendly URLs enabled.