Hey @StirCrazy,
@opnspaces is correct. You will first need to join the group to start a conversation. Once you have joined the green button should appear.
@opnspaces also brings up a point we are trying to correct now with the confusion of clicking "Forums". One of the items we are working on is removing the very long and large "Groups" dropdown menu. So to get to a specific group you can go directly to it from your "My Groups" on the home page or you can click "Groups" on the nav bar which will take you to the groups page. The goal being to simplify the process.
Thanks again, everyone!
