Old threads are never really the ‘Right Place’ they’re there as archive material to be read. Generally the correct form is to start a new post for your issue.
Have you not already asked this question a couple of times today in threads?
Please keep to this thread you started on the issue,
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/editing-group-activity-stream/
if no response by the morning give the post a bump, in the meantime keep searching and reading old posts as the solution might well have been covered already.
