If you want to find a group you're already in or a new group to join:
Click "Forum" in the left-hand menu.
Groups are listed on the right side of both the General and Local Forums. If you are currently in any groups, you will see your groups listed here. You can go directly to your groups page here:
If you would like to look for a group to join, click "Edit Groups". Then click the green "Find Groups" button.
On the Discover Groups page, you can browse existing groups to join.
You can also create a new group by clicking the green "Create a Group" button on the Discover Groups page.