You can participate in a datathon by navigating via the overview list (“Datathons” > “Datathons”) to the detail page of a datathon and using the “Join Datathon” button there.
There are two options to participate: As a single person or as a team. As an individual, all you have to do is indicate that you want them to choose this option. A team must be created in advance through the “Datathon” > “Create a Team” dialog. When the required information is filled in, your team is created and you can participate in the datathon by entering the team name.