Here is how to add more forums to your group:
1. Go to your groups homepage.
2. Click 'Manage Forums' from the 'More Admin Tools' link.
3. Click the blue 'Create New Forum' button.
4. Enter the forum title, description and select the privacy settings for the forum.
5. Click 'Save' when you are done.
6. Repeat the above steps for each forum you want to add.