Open the mod's zip (4wayreboot-MIUI_1.8.26.zip) and the attached zip (System_appO2x.zip) side by side and drag the "system" folder from "4wayreboot-MIUI_1.8.26.zip" into "System_appO2x.zip". Rename "System_appO2x.zip" to 4wayreboot-1.8.26.zip (or however you like), put it on SD card and flash...