Licenses assignation is made by the application automatically. The first license is assigned from the start to the user that installed the application. Then, every time a contact list is shared with a user, a new license will be used. When you share a contact list/label with a Domain Group (Google Group) each member of the user's group will consume one (1) license.  Note: If you share with more users than your number of licenses, the new ones will be marked as "Unlicensed".  You can easily buy more licenses on your subscription page by clicking on 'Add Licenses'.  You can liberate a license from a user and transfer it to another user by simply removing the invitation of the first user from the labels that are shared with them.