Every group on Count.It gets a custom invite code. Group Admins have access to the code, and can give it out as they see fit. To join your group, your friends or colleagues will download the Count.It app and create an account. During account creation, they will be prompted to enter a group invite code. When they enter your code, they will be able to join your group!
Once in your group, a person can join any active or future challenges. If they join a challenge that has not yet started, they will simply be placed in the "Starting Area" with all other challenge members, and they will see a countdown clock showing the time left until the challenge starts. If they join a challenge that has already started, Count.It will attempt to sync their activity data back to the start of the challenge.
Any group admin can access the group invite code by tapping on the "+Invite" link on the group Home screen, or on via Group Settings --> Invitations screen:
Tap on the Invitations option to get the Invitations screen:
Simply tap the "share" icon, and then copy the code, or send it via your mail, message, or any other app on your phone.
PRO Tip: Premium subscribers are not charged for days before the challenge has started, or after it is over. They are only charged for active challenge days. So, there is no charge for users simply being a member of a past or future challenge.