Currently i don't think you can. All sitemap plugins only include the base page of wpForo (example: community), and nothing else.

I think there is nothing you can do about it. Unless wpForo includes it at some point, but don't hold your breath ....

Not sure why you need in 2017 a sitemap, if you explain your problem maybe we can help. If you need to facilitate google to index your post, you can include widget for recent post/topics in your Home page footer.

I want to my forum will be referenced on google and another search website.

The one important thing is to have a sitemap XML for this.

What widget you talk ?

My home page is the forum.

Sitemaps only make the life of search engines easier, nothing else. Google is perfectly capable to index your site without a sitemap.

About the widget: in order to make indexing easier, the Recent posts and Recent topics widget do that exactly: help google to index new posts quicker.

All-in-all, sitemaps are a legacy method, imho. Your forums will be fully indexed (slowly or fast) depending on your total image in the eyes of Google. If you worth it or not.

wpForo forum is a categorized link directory. It's too easy to index for Google bots. You don't need any sitemap. Just give the forum root URL to Google and it'll index whole forum within 1-2 weeks. We have dozens of examples of success indexing without any sitemap.

I'm sorry but wpForo topics and posts are no included WordPress sitemap plugins, they only collect WordPress post types. wpForo topics and posts are not WordPress post types.