If you are a Supervisor, you can create a new account for a colleague from your 'Account' section, by clicking on "create a new user".
You must provide his full details - he/she will then receive an email with login details.
Please note that this feature is subject to your billing plan (ex: if you selected a plan for max. 5 users, you will obviously be unable to create a 6th user - and will need to upgrade your account to do so).
