Once you are an organizer, you have access to the group's participate page, where you can access the group's discussion board, action list, and organizer list, as well as create actions sponsored by that group.
Click the "Discussion" tab under the main section to access the group's private discussion board. Only group organizers and administrators have access. Type a comment and click "Post To Discussion Board" to post your message. All group organizers and administrators will be emailed your post, along with a link to respond.
Discussion board comments are listed chronologically, with the newest first. You can reply to a comment by clicking the "Reply" link under the comment you're interested in.
The discussion board is turned off by default, if you want the discussion board to be available, navigate to the 'Settings' tab and under 'General Settings' check the 'Enable group discussion board' option. This will enable the discussion board and add the tab to your group manage page.