Answer ID 4333
The new SHIELD TV supports external USB flash drives and hard drives.
If you have a Network Addressable Storage (NAS) you can mount it to your SHIELD TV in Settings > Storage & reset
To expand your internal storage for apps and games, your USB drive will need to be set up as internal storage. Go to Settings -> Storage & reset -> Select the drive name, then select the "Set up as internal storage".
SHIELD TV (2015), SHIELD TV Pro (2015) and the new SHIELD TV Pro also include a microSD card slot for expandable storage.