Also see: Help:Start a new community like Tupka mentioned.
i have a new wiki, how do i add forum?
You cannot. Forum, as in the feature we are currently using, is being retired. Its replacement is Discussions which should already be enabled on your wiki.
how do i add discutions on my wiki, wof fan wiki
Please create a new thread for this. Also, link to which wiki you are talking about. There are a lot of WoF wikis in your favorites list and I have no idea which one you are talking about.