From a PC, you can access internal and USB attached storage on your SHIELD TV.
To transfer content to your SHIELD:
Connect your SHIELD to a computer using the supplied micro USB cable plugged into the micro USB port on your SHIELD.
Use a file explorer on your PC to identify your SHIELD device and click on your SHIELD device name.
NOTE
For convenience, ensure that the type of content you copy from your computer
to your SHIELD matches the folder name. For example, copy movie
files to the "Movies" folder and music files to the "Music"
folder.

Your SHIELD TV can become discoverable as a network addressable device.
Under Settings
> Device > Storage
& reset, select "Over Local Network."
The following page will have the information needed to log into your SHIELD TV to transfer files in and out of your storage.