You can add new users to your organisation. All you need is their email address.

How to do it

You must be an Organisation Admin in order to invite someone to your organisation’s account in this way.

Select Settings in the left sidebar.
Select Colleagues and choose Add a Colleague
A popup appears. Enter their email address. You can add multiple email addresses by separating them using a comma( , ).
Use the dropdown menu to choose the role you’d like the person to have on each project. All the user will have the same permission on the projects that is selected.
Press Save
The person will receive an email containing instructions to login to Makerble and access their user account.
If you need this person to be an Organisation Admin, Project Creator or Organisation Member, you can go to your Colleagues per Project page to grant them the appropriate role: Give a colleague Organisation Admin access
If this person needs to have access to Albums and/or Progress Boards, you can grant them access from the respective 'manage' pages:
1. Manage colleagues' access to Progress Boards
2. Add, manage and remove colleagues on Albums

Alternative option - via a Progress Board

You can invite a new person to your organisation by first inviting them to join one of your Progress Boards, as outlined here Add users to a Managed Progress Board
Once they have joined your Progress Board, they will be listed on your Colleagues page. From here you can assign them to projects and albums using the respective tabs.