An organization turns individual accounts into a team. It all lives in Settings under Organization → Members & sharing.
Create one
Click "Create Organization", give it a Name and Description, and you're its admin.
Joining one
You join an organization by invitation. An admin invites you from inside it, and the invitation arrives by email — there is no way to find an organization by name and ask to be let in, because that would mean every customer could search every other customer on the platform.
Invite people
Admins use "Invite User To Organization": enter an email and pick a role — Admin to help run the organization, Analyst for day-to-day GIS work, or Viewer for read-oriented access.
Invitations you're sent appear in your own "Pending Invites For You" panel.
What each role can do, on shared work and on Tamaat Server, is on one page: Roles and Permissions.
Manage licences
"Organization Members" lists everyone and whether they hold a licence. Use "Assign license" and "Revoke license" to move seats around as your team changes — when Ava Reyes joins the buildout team and a departing contractor's seat frees up, that's this panel.
Set the sharing policy
"Sharing Policy" decides how far members can share, and you set it separately for projects, layers, and layer groups: "Organization users only", or "Any platform user".
Keep it at organization-only where work has to stay in the team. Widen it only where people genuinely need outside collaborators. When the policy blocks a share, the Share dialog explains why — see Collaboration and Sharing.