All event and customer data will exist within an organization. A site user or "portal" user has permission to view and edit any items owned by an organization. A portal user can view all data when initially logged in. However, a portal user may also go "into" an organization to view just that organization's data.
To enter an organization, go to the Organizations list and click on the name of the organization you would like to enter. When you do this, the navigation menu will change and show the name of the organization above the list of menu options (see image below). This lets you know that you are viewing information related to that organization.
You can navigate back to view all data in your portal site, click on the Organization list and the menu will update.
Menu when acting as site user
Menu when inside an organization
Another option for viewing an organization is available if you have a user that belongs to an organization. If you are a member of an organization then you can use the account options on the top right to switch your user identity. You can then switch back to your portal user to view all data again.