How to root Bluetimes 3584F Android TV box?

I need to move the apps to SD card because the internal memory is almost full, but I can do that only if it is rooted. So, I need to root my Android TV Box, Bluetimes 3584F.

This is the firmware link to download and the guide as install it on Android TV Box: firmware_Bluetimes_3584F.zip

Upgrading guide:

1. Unzip the downloaded firmware file, you will get 4 files named "g18ref-ota-XXXX.zip", "factory_update_param.aml", "u-boot.bin" and
   "recovery.img".




2. Copy the 4 files to the root directory of your SD card.




3. Take off the power adapter from your media player and insert SD card to the card reader slot.




4. Press and hold the reset hole on the back of the media player(beside the power socket), then connect power adapter to this
   item, still holding the reset hole



5. When you see the upgrading process bar showed on your TV screen, you can release the reset hole.

After firmware updating finished, TV box will reboot automatically.

I appreciate any help.