Single account on License server may create unlimited Users. Users page allows invite other users to your account. Each user within a single account have an access to both make new and edit existing subscription as long as managing the billing info.
The way for creating a new user as same as any customer os user account in ThingsBoard PE. Press Add User , fill the required fields and send the Activation link to the user.
Within User management page you may log in as particular user or delete the user also.