Creating an Organic Group is something that must be done by a site's Architect.  There are at least two, and sometimes three, different main components involved.

Following is a brief overview of these components.

Click on an image to make it bigger.
D7 - OG - Set Up - Group Dashboard

1. Group Dashboard

The Group Dashboard serves as a hub for the group.  Here is where a filtered list of group content is made available which a group manager can exercise bulk operations on for rapid content management.  Additionally, you'll find other group related blocks, such as the Mission Statement block, the Contact Info block, and the Google Map block. These are all items that are associated directly with the group and managed via the group as well. 

D7 - OG - Set Up - Group Landing Page

2. Group Landing Page

The Group Landing Page is what could be considered the front page for your specific group.  This particular page displays group navigation, the Feature Story Rotating Header block, any media feature blocks that may be in use, job posting information if available, news and events blocks, and the contact information block.

D7 - OG - Set Up - Parent Landing Page

3. Parent Landing Page

The Parent Landing Page is not used with every site.  It's only used when a nested group structure is required  A good example is a large organization that might have several different departments, which contain several smaller units, such as the Information Services site.