1. Download APK first, then copy to your Android device's SD card

2. Install APK, DO NOT open app

3. Download obb files, then rename to 'main.122.com.shakkarakkarash.rivalityzombieattack.obb'

4. Copy obb file to /SDCARD/Android/obb/com.shakkarakkarash.rivalityzombieattack/main.122.com.shakkarakkarash.rivalityzombieattack.obb