What does it mean to "authorize" the OverDrive app?
You need to authorize the OverDrive app (for Fire tablets, iOS, Android, Chromebook, and Windows 8/10) to download and read Adobe EPUB ebooks.
You automatically authorize the app when you sign in with any sign-in option. Learn about which sign-in option is best for you here.
If you use the OverDrive app on multiple devices, always sign into each one with the same account. That way, the authorization will match and you'll be able to download the same ebooks on each device.
Note: If you sign into the OverDrive app using the under-13 option, you can only download ebooks to one device. Learn more about app sign-in options for users under 13 here.