The organization is the highest level, in fact it is the container for applications. You can create an organization and manage the membership.
Go to My Organizations and click the button
The newly opened modal requests that you provide information for the new organization:
Provide name, description and indicate public or private accessibility.
Ready? Click Create Organization.
The new organization is created and is listed under My Organizations.
As you are the creator, you have the role of 'Owner' and enables you to manage membership.