Anyone can join a Public Room once it's set to public. The rooms will appear in the "Public Room" category on the homepage. It looks like this:
Since anyone can join these rooms, it's important to be a diligent room host. Check the Content Controls section to learn more about the features you can implement to better moderate your room.
You're also competing with other rooms on the Public Rooms page, so if no one joins your room right away, be patient. There are other rooms people are joining. To encourage more people to join, include a bio for the Public Room. Learn how to add a bio in the next article.