Go to the Groups page. You will see all the available groups.
On desktop, you can see Groups link on the left-side menu.
On mobile, click the three-line Hamburger menu, and select Groups.
All available groups are listed on the page.
Public and Private Groups
A group may be set as public or private.
Public "open" groups are available to join immediately. Go to the Group's detail page and click JOIN.
Private "closed" groups require an application to join the group. Go to the Group's detail page and click APPLY.
About the application:
The application may be just one click submission or it may require answering three questions. (Additionally, the admin may state other criteria beyond the system settings.)
After applying, the application goes to the group admin's review. Upon admin approving your application, you will become a member of the group.