Unlike most other forum software that contains a UI to create polls in a thread, Discourse works in a different way. In order to create a poll, you must start the title of your thread with Poll: then, add a description of what the poll is about. Use the bulleted list button to add choices to the poll. Once you’re finished, hit the create topic button to see your poll. Note that the preview on the right will not show you the rendered poll but you can edit the post after it’s published to fix any mishaps.
To close the poll, click on the Close Poll button. When you close a poll, the title of the thread will automatically change to say Closed Poll:
It’s strange as their is no UI or indication of how to create a poll. I had to look it up on the official Discourse site to figure it out. At least now, we have a dedicated post explaining how it works.