There may be a conceptual problem here. RecordingsBN is actually a view for the recordings created by BigBlueButtonBN and not a plugin for creating recordings itself.
What you need to do is.
1. Add a BigBlueButtonBN activity/room to your course (which you already did)
2. Make sure the option "session can be recorded" is enabled for that activity/room. You'll find that option as an advanced setting by clicking the "show more" below "send notification". If you didn't change anything to the global configuration, this option comes enabled by default.
3. Save the activity/room, use the link that is shown in your course and join the session.
4. Once you are in BBB, make sure to press the button for recording that shows up in the tool bar. The capture will start at that point.
5. Logout from the session and once you are in Moodle again you may want to press the "End session" button. It is not required but it will speed things up for you as the recording is being processed until the session is closed in BBB. If any user remains in the session it is kept open.
6. Wait until the recording is processed, depending of the BBB server, the duration of the session, the resources you used it may normally take something between 6 to 30 minutes. (some times more if you are using test-install. This server is heavily used)
7. After that time, just refresh the page where you activity/room is. The recording should show up there.
Now on recordingsBN, well, once the recording is visible in BigBlueButtonBN you should be able to see it in the RecordingsBN list. As I said, the former is the source, the last is just a view. Although, in the Activity/Room you will see only the recordings for that specific instance of BigBlueButtonBN, while in RecordingsBN you will see the recordings for all the activities in that course.
I hope this helps.