Need help with USB

Feb 1, 2015
Recently, the Mi TV Box asked us to update to a new firmware version however I'm very unfamiliar with it. I'm trying to download apps (apk) via my external USB flash drive into the TV Box, but I can't seem to access it. The box recognizes the USB, but I don't know where to see the apk files I want to install. Help! Is there any way to revert to a previous firmware version, or any help for the current firmware version? I speak primarily English, so advice in English would be appreciated.