We've written this new document (attached) that we hope admins will find useful. It covers the same tools and processes discussed in the blog post A Day in the Life of a My Esri Admin, but in downloadable PDF format.
From now on, when a user is made an admin by being granted Administrator Assign Permissions permission, this document will be provided to them as a link in the invitation email they are sent from My Esri.
If you are already an admin, feel free to download this new PDF from this blog post.
Note that this document is currently only available in English; we are in the process of having it translated into the 30+ languages supported by My Esri.
[UPDATED 4/25/2019 to change the name of the permission formerly known as "Assign Permissions" to "Administrator".]