Do you need help the device after installing the ROM?
MIUI 8 for Oppo F1S: How to Install, Features, and Performance Review miui 8 oppo f1s
You cannot flash a custom ROM on a stock Oppo device. You must first unlock the bootloader and flash TWRP recovery using SP Flash Tool or Fastboot commands on your PC. Skip this step if you already have functional TWRP recovery on your device. Step 2: Boot into TWRP Recovery Power down your Oppo F1S completely. Do you need help the device after installing the ROM