Every group on Count.It gets a custom invite code. Admins can access this invite code via their Group Settings screen:

To invite people to join your group, simple tap the "share" icon, and then copy the code, or send it via your mail, message, or any other app on your phone.

Note: To join your group, your friends or colleagues must 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!