The best way to find documentation for what you need on this site, is to try it out. Most of the time you will be lead over to sections that show a use case like yours.
However documentation is being added every week. On the right you will find a guideline menu and a code/hooks menu with lots of usefull information.
The homepage has a teaser to how you can login under a demo user for instance Mickey mouse, making you member of the disney group and having friends like Donald duck. These character play helps in understanding why you see certain activity and some not.
Heartbeat streams with their configurations:
Issues from drupal.org that can help you customize your project.
- Connected Heartbeat not shown to anonymous users. This is about extending or overriding the ConnectedHeartbeat stream.