Thanks for purchasing the plugin. I assume you already have bbPress Private Groups installed, right? The bridge plugin works by checking all the users assigned to receive notifications in Admin -> Settings -> Forums -> Email Notifications, then compares it with the groups allowed to view the forum of the new message.
As long as your private groups are set up correctly and the correct role is checked under Email Notification settings (usually Participant), there’s nothing else you need to do.
Do let me know if you have any further doubts.