The portal is available only to registered and authenticated users. There are organisations and users, user may be a part of multiple organisations (typically one) and organisation may contain multiple users.
Before you start please ensure you have ABN of your business (or of the organisation you are planning to work with), business email address and your phone number.
To signup please fill the signup form and submit it. Once accepted you need to verify email address - by clicking the link in message sent to you. After that you can login to your account but you won't have access to any organisation by default - it must be approved by some staff member.
Once approved (you'll get the email notification) the documents UI and ability to work with API will be unlocked.