Account owners and account managers can add users from Control Panel -> Users. Each user signs in to the Web Portal with their own username and password, which is emailed to them when they are added.
A user's role controls what they can do in the Web Portal:
Read-only users are free. A user who can edit data (including importing sessions) uses a license, either one of their own or one shared with a device. When you add or edit a user, choose one of:
A device linked or created this way gets the user's username as its Unit ID, so the user enters their username as the Unit ID in the app. Account owners always use a license.
The Users list and each user's page show their license and linked device. The license allocation table on the Account page shows every license and how many are free; users without a device show a "Link a device" link there.