You may want to get rid of an outdated, duplicated or unneeded space. If you're the moderator of such a space, you can delete it from the app. When a space isn't moderated, its members can leave it at anytime. Then they don't see it anymore.
To eliminate a space, remove everyone from it, including yourself. When the last person leaves, the space gets deleted. You won't be able to retrieve any of the messages or shared files from the deleted space.
See Cisco Knowledge Base for detailed instructions