You have to be the owner of the organization to be able to delete it.
Deleting an organization irreversibly removes all your data. If you want to cancel your paid subscription and downgrade a plan to free instead, visit this page.
Quick access to your organizations is always available in your Dashboard.
You'll see a section for "My Organizations" and should see your organization listed there. To access the area where you can submit the deletion, you'll need to visit the "Settings" area.
When you arrive at that settings page, scroll to the bottom to see the instructions for deletion.
You must enter your current password and then click on "Delete Organization" in order for the request to be submitted.
Your organization and its data will be deleted. If you have a subscription it will be canceled immediately and you will no longer be charged.
Deleting an organization irreversibly removes all your data. If you want to downgrade a plan to free instead, visit this page.