: Create a complete system backup via TWRP, as all data will be wiped.
: The device bootloader must be unlocked to permit the installation of custom software. miui 8 oppo f1s
: Download a compatible MIUI 8 port for the Oppo F1s (often based on Android 6.0) and save it to your internal storage or an external SD card. How to Install MIUI 8 on Oppo F1s : Create a complete system backup via TWRP,