Here's how to add a poll to a post in a group:
1. While in the group you'd like to post a poll, click on the "Add a Post" button (just like you would if you wanted to post a new post to the group).
2. Click the "Add a Poll" link below the text box.
3. Scroll down the page and enter the question and options you would like in your poll.
4. Click the "Add Post" button when your poll and the rest of your post are complete.