The E-Mail " Demiplane GM’s Guide to your Adventure Portal!" has three links with super interesting sounding titles which sadly only points to a page at Zendesk stating “The company you’re looking for is no longer using our help center.”
You might want to fix that 
cheers!
Thanks for letting us know! I’ve passed it along so we can take a look at that email and make sure those links get updated.
Since those links in that email are still broken, is there any other source of documentation about how to use this platform, particularly how to set up and configure groups and access to those groups, private or public visibility, etc.
Hi there! We’re currently working to get that email updated, but in the meantime, these links should direct you to the pages it mentions!
Beginner’s Guide to the Demiplane Adventure Portal