Make sure that third-party apps are allowed on your device: go to Menu->Settings->Security->and check "Unknown Sources"
Download APK and OBB file and open the APK file, tap apk file, then hit Install and do not run yet.
After successful installation, you need to place OBB file in the place <shared-storage>/Android/obb/com.alphatikinc.raidfield2/main.9253.com.alphatikinc.raidfield2.obb
