As a manager you can add one or more users to your team.
This is done under the People & Teams tab in the dropdown that appears when you click on your account avatar in the top right corner.
Under 'People & Teams', inviting members can be done by clicking on 'invite members' in the top bar of the middle panel. It is possible to invite multiple users at once by entering their email addresses, separated by a comma.
Newly invited users will be marked as 'pending' and the manager can then add them to teams or folders.
When a newly invited user accepts his invitation, the manager receives a notification email that a pending user has onboarded. At this point, and for security reasons, the manager automatically be logged out and needs to login again. This will start the encryption process with the private keys of the new user. Otherwise, the workspace will remain empty for that user.