• Login to gmail account on ADT-1 device
• Go to Playstore on computer
• Login to Playstore with that same gmail account
• Choose No carrier Google ADT-1
• Hit install and then wait a few minutes for it to install on the device
• Go to settings - apps - Es file explorer open

You don't need to be rooted. With Es you can open an ftp connection then transfer files back and forth between your computer and ADT-1 device.

Bonus: This game also works with ADT-1

List of apps that have the option to be installed onto the ADT-1 Device

Modern Combat 5

Grand Theft Auto San Andreas

Wayward Souls

Leo's Fortune