If you didn't sign up your teammates when you first signed up to the Rally, you can do so by logging in here and going into 'My Adventures'. Here, select 'Members' and pop in their name and email. They will then get an email with instructions on how to sign up.
Doing this is important for a bunch of reasons, one of which being the excellent Cool Earth charity swag sent to each team. If your teammate isn't registered, you won't receive enough swag for all of you.