Open your organization in the Cockpit, then go to Settings (sidebar). The first tab is General — URL pattern: /o/{organization-slug}/general.
This section is labeled as basic details about the organization. You get a form with:
Only fields that are enabled can be changed; slug and ID are there so you can copy them when needed.
A separate card warns that deleting the organization also removes its projects. You should back up anything you need before deleting.
If the button stays disabled, hover the info icon next to it for the full explanation (e.g. active projects or subscriptions must be cleared first).
After a successful deletion, you are typically redirected away from the organization (e.g. to the home / organization picker).