How do I turn off the Pink Bar?

When I was signing up, it guided me through creating this pink bar…

But now I can’t figure out how to make it go away!

That is set by your admin. They’ve chosen to establish a Site-Wide Announcement, and it will persist until they delete it in their Pack Settings.

If you are the admin, it’s here: Manage > Settings > Edit Pack Settings > Site-Wide Announcement > Announcement.