To find a public group to join, open your OpenSports app, and go to the Groups tab (the tab with the icon of three people). Scroll to view all of the local public groups. You can also use the search bar to search for the name of a public or private.
You can click on the group to view more details about the group and request to join the group if you want to receive invites when they post new events.
On the website, you will see a few local groups in your area on the OpenSports Discovery page.