It's been confusing for me and others to know how to ADD A NEW TOPIC to our GROUP. This is different from Commenting on an existing post.

1. Hit  the red GROUP tab at the top.

2. Select your Group from the side bar list on the left in the bullet items, select My Groups

3. Once you're in Your Group you want to post you'll notice the side bar on the left changes

4. Select ADD POST TO GROUP

5. Title, Select your Audience, Go to the Body field and Save.

Hope this helps.