Connect to your device using adb connect IP_ADDRESS
IP_ADDRESS is the ip address of your FireOS device.
You can find your device IP address from Settings -> My Fire TV -> About -> Network
The first time you connect, your Fire TV will ask on-screen if you should allow this connection. Enter "yes and remember this device".
You may need to run the adb connect IP_ADDRESS a 2nd time if it took you a while to do the last step.
Run the needed commands (via adb shell)
adb shell appops set com.videostorm.splashtiles SYSTEM_ALERT_WINDOW allow