You’ll need to install and setup adb and then run the following commands. Change ipaddress to the ip address of the device running Android Things

adb connect ipaddress
adb root
adb remount
adb push bootanimation.zip /system/media/
adb reboot

bootanimation.zip will either need to be in the same directory as adb, or you can specify the path. For example if it is located on your Desktop you can use

For Windows

adb push \Users\username\Desktop\bootanimation.zip /system/media/

on Linux or MacOS

adb push ~/Desktop/bootanimation.zip /system/media/