If you have a Team or Enterprise subscription, the admin of your account can add Members by uploading a CSV file.
Click on 'Members' on the left side menu of the admin settings
Click 'Invite members' in the top right corner.
Select 'Import CSV file' in the pop-up window.
From here you can either upload an existing CSV file or view an example CVS file to learn how to add members.
The following scheme applies for the CSV file:
Email is a required column header
Name is an optional column header