War82, the answer depends on your theme.
Most likely, your theme will generate the links in the menu bar automatically from your pages.
In this case, the easiest solution for you would be to add a simple redirection plugin such as this: https://wordpress.org/extend/plugins/redirection/screenshots/ (first result if you search ‘redirect’ from the ‘add new’ plugin page in your wordpress installation)
Then you would just create the page “Community Forum”, copy the URL of the page (e.g. http://www.yourblog.com/community-forum)
With the plugin installed and the page created you would just go into the redirection plugin setting menu and add a redirect from the community forum url to your forum url (www.yourblog.com/forums by default)
Good luck
