So all is ok from wpForo site. I have nothing to add here. If you want, you can force indexing some topics or pages in Google Webmaster Tool, or just wait until they'll be indexed. In any case, there is nothing to do in wpForo.
In case you want to say thank you !) We'd really appreciate and be thankful if you leave a good review on plugin page. This is the best way to say thank you to this project and support team.