Instructions for Side Loading Libby on a Kindle Fire (a way around Kindle not being able to install Libby by default)
Go to Settings / security / Priv and turn OFF the “Apps from Unknown sources”.
Uninstall the OverDrive App (if installed).
Open this link on your Kindle Fire: https://apps.goodereader.com/android-apps/e-reader-apps/?did=39495
Click on the orange download button in the image on your device.
Install the app.
Go back to Settings / security / Priv and turn back ON “Apps from Unknown sources”.