The parent or main organization is set up as an account. If there are subsidiaries, those will be set up as child accounts. For instance, if Major Media owns multiple television stations or publications, Major Media would be set up as the main account. A child account would be created for every property.
If you have access to multiple accounts (such as child accounts), you may switch between those accounts by going to Settings in the top navigation bar. Click on the Switch Accounts dropdown menu to see a list of the accounts you have access to and switch between them.