BuddyPress.org

Please don’t bump your posts more than once every 24 hours.

To be clear, did you follow the steps from this page https://codex.buddypress.org/buddypress-site-administration/buddypress-forum/ , at the bottom where it reads Process for installing bbPress included with BuddyPress?
1) Dashboard > BuddyPress > Forum Setup
2) Setup a new installation, etc
3) Then go to a group > Admin > Enable group forums

You should then see a Forum tab in the group. The bbPress software comes autoinstalled when you download BuddyPress. There is no need to download anything else.