Unlike other formats such as the Games, you will sign up as a team at the onset of your registration and compete as a team from beginning to end.
When signing up for a team event, you should already know your:
Who's on your team (Name, their Email, Apparel Size)
You will want to consult with the Event Director of the competition regarding any specific rules in a substitution. In most cases, if you have a fallout with a team member, you can replace a team mate anytime before the first deadline of a workout. To learn more about how to manage this you can check out this FAQ.