As of writing this book, there isn't much to do to administer PowerApps or Flow. The screens are identical for administering both products, although they are separate admin centers, so we will cover both at the same time. Screenshots are all taken from PowerApps unless otherwise specified, but they look the same in Flow administration:
There are four basic areas you can work with: Environments, Data policies, Data integration, and Tenant settings. You might not have access to all of these areas; Environments, for example, come with PowerApps Plan 2 only.